Your point about productizing the scope, not just the price, is especially useful because a buyer can judge a deliverable before committing. One practical addition is a tiny acceptance checklist in the scope email: what files or fields will be delivered, what counts as complete, and what happens if an input is missing. It gives the client a concrete way to review the result and keeps a fixed-scope service from quietly turning into an open-ended task. The human approval rule for anything promising a price or date is a strong safeguard too.