I knew the chopper market would die as they are way overpriced for what they are. Most of the money is in labour to put them together. The sum of the parts don't add up to $70-80,000 and I don't really know how the labour does either. At the end of the day a chopper will always be worth less than a stocker.
As for the TT500's I wouldn't put them into the chopper/mustang basket. I owned one new in '76 and have followed the TT market ever since. It's grown steadily and has a cult following more so than fashion fad following. Although I'm sure their would be a few. It could just be the old supply and demand or it could be the economy. Fuels up, waters up. powers up, groceries are up, wages aren't so something has to give, and it's usually that bike taking up room in the garage that you don't ever ride. A fully restored XT500c did pull about 7K a few months back. But I have noticed the TT/XT market isn't as hot as it was a year or two ago, but a lot of other VMX bikes seem to be slowing as well. Moderns too, try selling your four year old dirtbike that you paid 13K for. Be lucky to get $6,000 for it if you can sell it at all.