I’ve never contracted as a developer, but a contractor friend has told me something similar happens with clients. They want a toilet put in and and inspect the $500 bill to see where the unnecessary expenditure is, and the client who wants a $50k bathroom remodel, just wires them the money as soon as they get the invoice.
I have experienced both, in seperate domains. But sometimes not always the $500 client saved up and probably dosent have lot, so that money is near and dear. The $50k client probably has more money and the $50k is not as big of an impact.