Yeah, very fair point on this. Are private secondary markets just by default eternal bull markets? What's the price correction mechanism? Devaluation due to massive supply/demand imbalances?
If the market is small enough and there isn't leverage, you can have long term price dislocations. (Example: penny stocks) If the purchases are funded by borrowing, then eventually the debt payment come due and force corrections.
Interesting space to get involved in, for sure.