Jerry hall of HPR makes a good one. Currently making HPR 19. Pretty sure its more than $400. Does not have a lot of bottom end loss that you find in the Aaen and Q V1.
Aaen is a QV1 copy for about $360. It has fitment issues and is not as good of quality as the Q pipes. Not as much bottom end as the fmf but WAY more mid and top end.
Dyno port makes a mid to top end pipe but be prepared to shell out more than $400.
CT Racing offers a mid range pipe and silencer,and an outlaw pipe and silenced for $420 with the option of "showroom floor" chrome for only $60.
Paul Turner or LRD makes or made a pipe but I'm not sure how much they are IF you can find one.
FMF... cheap, around $220 to $250 on ebay. If its anything like my 250 fmf, its a good trail pipe but lacks top end.
DG aka da turd. Id stay away from this one.
Dr Q has made several pipes but he didn't have the money to pay for a batch and that's when somebody else he was working on it with took over the Q V1 and the Q V2. Matt Shearer/SCP currently make the QV2. Ive heard the v1 lacks bottom end. The V2 I believe doesn't have this problem as much as the V1 and the V1 has issues of breaking the pipes mount. But that has been resolved. The V2 can be used for trail riding or MX. Be prepared to spend way more than $400.
What Ive learned is exhausts are not cheap. Top shelf pipes run from $500 to $750 depending on make and model and what kind of finish it has. I.e.chrome or raw. Chrome pipes usually run $150 more than raw. Some offer heat shields where as others don't. Ive heard on the zilla the pipe sticks out so much that a heat shield makes life a lot better. My advice is to save up till you can afford a high end pipe. Then later on down the road when it comes time to get the motor built by somebody, you wont have to buy another pipe. In the long run it saves money
The main 3 best are SCP, HPR, and The V2.0. Forgive me if there are others I haven't mentioned or if any of this info is innaccurate. I'm by no means an expert, just thought id try to help you out. Best of luck.
http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR8.TRC2.A0.H0.XLT+500R+pipe.TRS0&_nkw=LT+500R+pipe&_sacat=0