A software-as-a-service (SaaS) subscription looks cheap: a modest monthly fee per user, nothing to install, ready today. A custom system looks expensive: a large development invoice before anyone uses it. Yet over several years the picture can reverse. Comparing SaaS vs custom software properly means looking at total cost of ownership (TCO): every cost you will incur across the system's useful life, including the ones that never appear on the first quote.
The cost categories most people miss
Both options have visible and hidden costs. Listing them side by side is the first step.
SaaS costs
- Subscription fees, usually per user per month, sometimes tiered by features or usage.
- Tier upgrades: features such as single sign-on, audit logs, API access or advanced reporting are often reserved for higher plans.
- Add-ons and marketplace apps that fill gaps in the core product.
- Implementation and configuration, by your staff or a partner.
- Integration with your other systems, sometimes via paid middleware.
- Data migration in, and eventually out.
- Price changes at renewal, which are outside your control.
- Workaround costs: staff time spent compensating for features the product does not have.
Custom software costs
- Discovery, design and development.
- Testing and quality assurance.
- Hosting and infrastructure: servers or cloud resources, databases, backups, monitoring.
- Third-party services: email delivery, SMS, maps, payment processing.
- Maintenance: bug fixes, security patches, framework and library upgrades.
- Enhancements as the business changes.
- Knowledge retention: documentation and continuity, so you are not dependent on one person.
How the costs behave over time
The two models have different cost shapes. SaaS is mostly an operating expense that recurs and grows with users. Custom software is front-loaded, followed by a lower but steady maintenance cost that does not depend directly on user numbers.
| Driver | SaaS | Custom software |
|---|---|---|
| Year one | Low to moderate | High |
| Later years | Similar or rising | Lower, mostly maintenance and hosting |
| Adding users | Cost rises per user | Small infrastructure increase |
| Adding features | Wait for the vendor or pay for a higher tier | Pay for development |
| Price control | With the vendor | With you |
The point where cumulative custom costs fall below cumulative SaaS costs, if it ever comes, is your break-even. It arrives sooner when user numbers are high, and may never arrive for small teams.
A simple SaaS vs custom software model
You can build a useful comparison in a spreadsheet. Use your own quotes; the structure matters more than precision.
- Choose a horizon, typically five years, the realistic life before a major rework or re-procurement.
- Forecast users per year. Growth assumptions drive SaaS cost heavily.
- SaaS column: per-user fee × users × 12 for each year, plus tier upgrades, add-ons, integration, implementation in year one, and an allowance for renewal price rises.
- Custom column: build cost in year one, then hosting, third-party services and annual maintenance for each year. Maintenance is often estimated as a percentage of the original build cost per year; ask your developer for a realistic figure for your system rather than relying on a rule of thumb.
- Add internal costs to both: staff time for administration, training and any workarounds.
- Sum the columns cumulatively and see where, if anywhere, they cross.
Then run a pessimistic case for each: SaaS prices rise more than expected; the custom build overruns and maintenance costs more. If one option wins under both cases, the decision is clearer.
Costs that are hard to put a number on
Some important factors resist spreadsheets but should still be weighed:
- Fit to process. If the SaaS product forces you to work in a way that slows staff or frustrates customers, that cost is real even if unmeasured.
- Vendor risk. Products are discontinued, acquired or re-priced. Check export options and contract terms.
- Data ownership and location. Some industries and jurisdictions have rules on where data may be stored.
- Speed to market. SaaS can be live in weeks; that head start may be worth more than long-run savings.
- Competitive advantage. A custom system can embody processes competitors cannot buy off the shelf.
- Responsibility. With custom software, security and uptime are your responsibility, or your provider's under contract.
The often-overlooked third option
Self-hosted open source applications sit between the two. There is no licence fee per user and you control the data and code, but you take on hosting, updates and support, either in-house or through a partner. For some categories, such as CRM, helpdesk, e-learning and file sharing, mature open source products exist and can be extended rather than built from scratch. See our open source solutions for how that route is costed and supported.
Practical guidance
- Small team, standard process: SaaS almost always wins on TCO.
- Large or fast-growing user base: per-user fees compound; model custom or open source seriously.
- Unique, revenue-critical process: custom may be justified even at higher cost.
- Unclear requirements: start with SaaS to learn what you need, keeping your data portable for a later move.
If you want a second opinion on the numbers, a TCO review is a typical software consulting engagement. Hosting is a significant line in any custom model, so ask a cloud solutions provider to size it realistically rather than guessing.
Key takeaways
- Compare total cost of ownership over three to five years, not first-year price.
- SaaS costs recur and grow with users; custom costs are front-loaded with ongoing maintenance.
- Include integration, migration, internal staff time and workarounds in both columns.
- Weigh fit, vendor risk and data control alongside the numbers.
- Consider self-hosted open source as a middle path.