It's a tough question, but speaking as someone who's been working on the lower scale of things and trying to increase my rates I'd say stick at your current rates. It's very hard to charge a client more than what you charged them for the same service at an earlier stage. If it costs a guy 1K to do 4 tracks with you, he won't be happy when 6 months down the line he comes back and you're charging him 1.6K to do another 4. You also don't want to end up in a situation where you're putting out work with your name on it that you aren't totally happy with. Working with lower quality bands, spending less time than you'd like on projects will definitely lead to a drop in quality.