Isn't it just a simple cut, weld and paint job? Several grand is ridiculous and outright robbery. Performance shops tend to be cheaper than body shops since the masses always go to body shops and get taken advantage of. I wouldn't pay more than $200 for the cutting and welding and not more than $100 per side to do the painting. They might use bondo filler on the outside crease and wet sand but that's easy...anyone can do that. You have to break everything down otherwise they sock it to ya. Good luck finding a place that's reasonable and honest, hard to find these days.
Before you have any custom work done always ask what their hourly rate is anonymously over the phone BEFORE you go in. That is very important. In Vegas where I used to live, the rate was $65/hour. In Los Angeles it's $85/hour. So if they tell you $1000 for 5 hours work then something is wrong. Don't ask how long it will take either...they always take their time, like twice as long as it should take if they really are "professionals". And paint "drying time" doesn't count as working time either lol. You have to stand right outside the garage and watch them and make sure they work fast. Bring a whip j/k. That's what I do and that's why shops hate me. hahaha. If you don't want to seem like a dick to them, prepare to pay a lot. And that's the bottom line.
If you don't want to be too tough and you want to feel like you're giving to the charity of the poor ass perfomance shops...let it go at like a grand, not a penny more.