I can give a funny example from past a few days. I was doing an research on Voice Over recording options here and there, quoting companies and people for the project we do. Some of them had give me their price, some not, some asked for more details etc... I've made my choice and machine started to go on... And after a couple of days one of the companies I quoted but not selected started to... renegotiate the price. They were asking for 'my preferred price' and some other things. They finished on "we will overbid anyone with 30%". Quite interesting, somewhat funny, spoken a bit idly... but my point is that the process of fixing the price is dynamic and when people starts to bid each other it can end far below a real value of their work.
I actually agree and disagree with Calum Bowen saying
I think one of the main problems is that a lot of people who give quotes are hobbyist musicians or aren't relying on music for livelihood