Why hourly is a poor fit for a build
Hourly billing puts all the uncertainty on the buyer: when the work runs long, every extra week lands on you, and you cannot budget for it.
Why a quick fixed quote is no better
A fixed price quoted before the work is understood is a guess. Either it carries a large buffer, or the gap comes back later as corners cut.
The sequence that works
Look first. The free audit ends in a written scope with a cost range, so the first number you see is one that can be stood behind rather than one invented on a call. The build is then fixed scope at a fixed price, starting with a working production slice inside two weeks and continuing in weekly increments on staging you can watch.
After launch
Running and improving the system afterwards is different work, better suited to retained capacity: monthly, sized to the estate it looks after, and cancellable on a month's notice.