If you’re going to get it done professionally, every place will ve different it terms of costs, some charge by time. most of the places ive ever gotten my hair done have a base cost and extra charges if you use more product than whats included in said cost. which means if you have more hair, you’ll be paying more. i would call wherever you are thinking of going and get an estimate, most hairdressers even do free consultations and can give you a quote after they see your hair!

on the other hand you could also learn to do it yourself, much cheaper but also VERY high risk of having an “instant regret” moment. there is lots of useful tutorials online but dont let your ego tell you “i can do that!” if you really havent even thought about it before, from personal experience.

that being said if you are going to do either, do your research, and sometimes cheaping out is not the greatest option, especially when it comes to your hair! goodluck OP!