Start with the work the system must do
A subscription price and a development quote cover different things. Before comparing them, write down the workflows, integrations, number of users and support you need. Ask each supplier to price the same scope, including implementation and ongoing operation.
There is no universal multiplier that turns a SaaS subscription into its total cost. There is also no guarantee that custom software will cost less. The answer depends on your requirements, contracts and the work needed to keep the system useful.
What to include on the SaaS side
Use the plan and terms you would actually buy. Check which features are included and whether limits apply to users, storage, transactions or integrations.
- Subscription fees for the expected number of users
- Implementation, data migration and staff training
- Paid add-ons and integration development
- Support costs and internal administration time
- Contract renewal terms, data export and the cost of leaving
Use your invoices and the supplier’s written terms where possible. If future headcount or usage is uncertain, calculate several scenarios and label the assumptions.
What to include on the custom software side
The initial build is only part of ownership. A useful comparison also includes hosting, support, security updates, backups and changes as the business evolves.
- Discovery, design, development and acceptance testing
- Data migration, integrations and staff training
- Hosting, monitoring and backup storage
- Maintenance, dependency updates and incident support
- Future feature work and a handover to another developer
Confirm who owns the source code, where it runs and what support the agreement includes. Do not assume maintenance becomes free after launch or that every future change belongs in the original quote.
Compare the same three-year period
For each option, add the initial costs to the recurring costs over 36 months and the separately priced changes you expect. Keep internal staff time visible rather than mixing it into supplier invoices. Record the source of each figure and flag estimates.
Then test how the comparison changes if the team grows, an integration becomes more complex or a supplier changes its renewal price. These are planning scenarios, not predictions. A small difference between totals may matter less than reliability, delivery time or how well the software fits the work.
When each approach makes sense
SaaS can be a good choice when an existing product covers the requirements and its terms are acceptable. Custom software can make sense when a distinctive workflow or integration cannot be handled well by the available products. A combination may be the most practical option, using existing tools for standard functions and custom software for the work that needs it.
Base the decision on documented requirements and comparable quotes. Without those inputs, a claim that either approach is always better value is not evidence.