Schecter has the Omen-8 at $400 and there is the ESP/LTD H-338 for right at $500 but those are the 2 least expensive 8 strings I've seen.
I HIGHLY suggest trying one before you buy one...7 and 8 strings are not my bag (I have enough issues with a 6 string!) but I recently played an Omen 8 just because I saw it and had to try it...