of course there is..and there are actually a lot of courses for this too..most people don't know how negotiate contracts or quote higher prices..usually because they are afraid of losing the contract..so they take whatever they get...the genuine course I found that deals with this problem was the one called "client acquisition system"...teaches everything from getting the clients..negotiating terms and charging the right price..by Eva Gutierrez..she used to write on Medium regularly...now she doesn't..but I have heard great things about her course and that it's genuinely helpful..I haven't taken it yet..you can check it out here..

https://www.eva-gutierrez.com/cas

And this is not an affiliate link and I don't know her in any way..it's just that i have a bullshit radar for shitty courses and her course happens to be one of the good ones..🤗