baseball had its 90s insert craze happen a few years back. It went gangbusters just like basketball 90s inserts are doing today. In my opinion the baseball collectors have had their fill and are now quiet. Plus in baseball, there are so much to chase down for PC collectors. Those who needed and wated it for their PC's have now picked it up which helps settle the market.
In my opinion the Basketball 90s craze especially on the PMG reds has more to do with very few PC collectors battling it out against Speculators/investors who are looking to flip it for $$. When a card like the Jordan PMG goes from a $2k card to selling for $11k in less than a year, it will attract those looking to make a dime off flipping cards. The two types of bidders duel it out and you get these crazy prices. You can tally it up to demand!!