$50 per pre-loop minute here, all (mostly) to NES spec. Can't export in system / assembly-level - can only do mp3s (and Impulse Tracker or other digital module formats, if you're able to loop into that code-side). For reference, if I were to compose, let's say, Megaman 5's soundtrack for the first time, it would cost you around 1200 bucks - that would be like 28-odd tracks, 45-50 seconds before they loop.
www.soundcloud.com/swerdmurd - can't budge much on the base price, but would be happy to help out if this works. Would be down to consult sound-needs side / sound design side of course
-swerd / Dan