7 months is a long time to dedicate to a game .. especially when you can't effectively 'pause' it. How many other facebook games do you still play after 7 months? So maybe there aren't that many active upper level players.
As for the transfer market, I hardly ever see any players worth buying. They have to be 54 (nearly 6*) to be better than what I have .. and AMs are extremely hard to come by. I still see a lot of auctions go 15-20 rounds still, but more typical is 5-12. Another way of looking at it is that maybe those players still active at our level are a bit smarter than average and so don't get into the bidding wars.
I still see about the same percentage of active teams as I did at level 4 ... so who knows?
There are many full active players in upper levels, specially above levels 24-25 competition is very hard.