Most businesses buying custom software for the first time get the pricing model wrong before a single line of code is written. Not because either model is bad, but because each one fits a different kind of project, and vendors rarely explain the difference honestly.
Fixed scope: pay for a destination
A fixed-scope contract means an agreed specification, an agreed price and an agreed date. It works brilliantly when you can describe the finished product precisely: an ordering portal for your retailers, a booking system for your clinic, a driver app with five screens.
The catch is that precision cuts both ways. Anything not written in the spec costs extra, so the quality of the scoping phase decides everything. A good vendor will spend real time mapping your workflows before quoting; a bad one will quote in an hour and recover the difference later through change requests.
Retainer: pay for a direction
A monthly retainer buys you a standing team and a prioritised backlog. It fits products that keep evolving: a live platform that needs new features, integrations and maintenance every month.
The risk here is drift: months of billing with no clear output. Protect yourself by requiring working software demos every week or two, a written backlog you control, and the right to scale down with 30 days notice. Any competent studio will agree to all three without hesitation.
The questions that protect you in both models
Who owns the code and the infrastructure accounts? (The answer must be: you, in writing.) What happens in the 30 days after launch when the first real-world bugs appear? Can you speak directly to the engineers, or only to an account manager? And can they show you a comparable system already running in production?
A vendor who answers these four questions quickly and specifically is worth shortlisting. One who gets vague is telling you something more useful than any portfolio ever will.
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