Buyer's guide
Custom software vs. off-the-shelf SaaS: how to decide
By Nick McCandless, founder of EltherionLast updated
The short answer
Buy SaaS when a mature product already fits most of your process and that process is not what sets you apart: it is faster and cheaper to start. Build custom software when the workflow is your competitive edge, when no product fits without constant workarounds, or when five years of subscriptions and integration work would cost more than owning the system. Many businesses end up in the middle, buying the standard tools and building a thin custom layer that connects them.
Side-by-side comparison
| Criterion | Off-the-shelf SaaS | Custom software | Hybrid: SaaS plus custom |
|---|---|---|---|
| Cost | Off-the-shelf SaaSLow upfront. You pay a recurring subscription, usually per user or by usage, so the bill grows as you add people and features. | Custom softwareHigher upfront than a subscription. Typical US agencies charge $60k to $150k for an internal tool and $120k to $300k for a customer-facing web app; Eltherion projects start as low as $1,000. Plan on about 18% of the build per year to maintain. | Hybrid: SaaS plus customSubscriptions plus a smaller custom build that connects them, often the most affordable way to get exactly what you need. |
| Time to launch | Off-the-shelf SaaSDays to weeks, mostly setup, data migration and training. | Custom softwareMonths. In our experience a focused first version takes three to six months. | Hybrid: SaaS plus customWeeks to a few months, depending on how much custom work sits on top. |
| Flexibility | Off-the-shelf SaaSYou configure what the vendor allows. The roadmap is theirs. | Custom softwareBuilt around your process, and it changes whenever you decide to fund a change. | Hybrid: SaaS plus customStandard where that is fine, custom where it matters. |
| Ownership and IP | Off-the-shelf SaaSYou license access to the provider's application. You do not own the software, so check the data export terms before you sign. | Custom softwareYou can own the code and the data, provided your contract assigns the copyright to you in writing. | Hybrid: SaaS plus customYou own the custom layer. The vendors still own their platforms. |
| Maintenance | Off-the-shelf SaaSThe vendor handles hosting, security patches and upgrades. | Custom softwareYour responsibility: updates, hosting, monitoring and fixes, either in-house or through a partner. | Hybrid: SaaS plus customShared. Vendors maintain their products; you maintain the integrations, which need attention when vendor APIs change. |
| Risk | Off-the-shelf SaaSPrice changes, feature changes or a product shutdown are outside your control, and switching later can be painful. | Custom softwareDelivery risk: scope creep, budget overruns or a team that leaves. Phased scope and good documentation reduce it. | Hybrid: SaaS plus customDepends on vendor APIs staying stable, and on someone owning the glue code. |
| Best fit | Off-the-shelf SaaSStandard functions such as accounting, payroll, email and a typical CRM. | Custom softwareWorkflows that differentiate you, products you sell, or processes no tool fits. | Hybrid: SaaS plus customGrowing businesses whose tools work individually but not together. |
01
When off-the-shelf SaaS is the right choice
SaaS is software you rent rather than run. In the U.S. government's standard cloud computing definition from NIST, the customer uses the provider's application but does not manage or control the underlying infrastructure or even individual application capabilities, apart from limited configuration settings. That is the trade: someone else carries the engineering, and you accept their product decisions.
For most standard business functions, that trade is a good one. Accounting, payroll, email, calendars and a typical sales pipeline work much the same way in every company. Paying a vendor who spreads the engineering cost over thousands of customers is almost always cheaper than building your own version.
Good signs
- The process works the same way in most companies in your industry.
- You can name two or three products that already cover most of what you need.
- You need it running this month, not next quarter.
- Nobody on your team wants to own software after launch.
- Your seat count is small and not expected to grow quickly.
02
When custom software is the right choice
Custom software earns its cost when the way you work is part of why customers choose you. If your scheduling, pricing, fulfilment or client experience is genuinely different, forcing it into a generic tool means either changing what makes you better or paying people to work around the software every day.
It also makes sense when subscription costs scale faster than your business does. Per-seat and usage pricing can be cheap for ten users and expensive for two hundred, and every extra tool adds integration work. Running the five-year numbers, not the first-year numbers, is what shows whether owning the system pays off.
Good signs
- Your team runs the process across three or more tools plus spreadsheets.
- Staff spend hours a week on workarounds or copying data between systems.
- You are building a product to sell, not just a tool to use.
- You need control over where data lives or how it is handled.
- Subscription costs at your projected headcount exceed a build plus maintenance over five years.
03
When a hybrid is the right choice
The hybrid path is the one most build-versus-buy articles skip. You keep the commodity tools, such as your accounting system and CRM, and build only what is missing: an integration that removes double entry, a customer portal, or one workflow the tools cannot handle.
It usually has the best ratio of value to cost, because you only pay for custom engineering where it changes the outcome. The catch is that integrations depend on vendor APIs, so someone has to own and monitor them.
Good signs
- Each tool works on its own, but data does not flow between them.
- One specific workflow is the bottleneck, not the whole system.
- You want to prove value with a smaller build before committing to more.
Run the five-year math, not the first-year math
The fairest comparison is total cost over three to five years. For SaaS, that is the subscription at the seat count you expect in the future, plus price increases, plus any integration work. For custom software, it is the build, plus maintenance every year, plus hosting.
Here is how that plays out with the default inputs in our build vs. buy calculator: a $60k per year subscription growing 15% a year, with $25k of integration work, against a $250k build at typical agency prices, maintained at 18% a year. Over five years, buying costs about $430k and building about $475k, so at agency prices, buying wins. Building pulls ahead when the subscription is larger, grows faster, or the build costs less. That last lever matters: Eltherion projects start as low as $1,000, so a focused custom build often beats years of subscriptions. These are illustrative inputs, not data about any real vendor, so put in your own numbers.
Questions to ask any SaaS vendor before you commit
A few questions protect you from the most common regrets:
- Can we export all of our data, in a usable format, at any time and when we leave?
- How has pricing changed for existing customers, and what is the renewal increase policy?
- Which features are on the plan we need, and which require the next tier up?
- Is there an API, and what are its rate limits and costs?
- Where is our data stored, and what security and compliance documentation can you share?
Honest advice
When not to hire a firm like Eltherion
We build custom software for a living, and we still tell many people not to. You probably should not hire us, or any custom development firm, yet if:
- A SaaS product already covers most of your process and you have not tried it with real data.
- An existing product already does what you need for a fair subscription price. Then buying it is the smart move, and we will tell you so.
- You have not confirmed that customers want the product. Validate demand first, even manually.
- No one in your business will own the software after launch. Custom software needs an owner, even when a partner maintains it.
Decision checklist
Work through these before you sign anything, whichever way you are leaning.
- 01List the five workflows the software must support, ranked by how much they matter to customers.
- 02Trial at least two SaaS products with your real data, not a demo account.
- 03Price each SaaS option at the seat count you expect in three years.
- 04Confirm you can export all of your data in a format another system can import.
- 05Ask honestly: is this workflow part of why customers choose us? If not, lean toward buying.
- 06If you build, budget for maintenance every year, not just the build.
- 07Name the person who will own the software internally.
- 08Check whether a hybrid (buy the core, build one integration) solves most of the problem.