This is a shameless repost of something I wrote at another forum but I think it applies here:
My hypothesis on this has a couple of factors.
1) Retrogaming has increased in popularity with people in the 20s-40s who have more disposable income
2) Youtube personalities promote videos that drive interest in "hidden gems"
3) People remember when you could get the games cheaper and everyone knows prices have gone up a lot in the last several years
I propose, that it is mainly people who have been collecting for awhile and have had "backburner" titles they meant to pick up or hoped to find in the wild, but have seen prices rise so quickly and drastically that they are willing to pay higher and higher prices now, just to lock in owning a title before the price escalates even further.
I can speak to this of my own experience, as there are lots of titles I was hoping to find in the wild (such as Warsong) that I know I will never find cheap in the wild at this point since I'm fighting an army of resellers in my own area alone. I've debated a couple times just saving the cash for awhile and shelling out for a copy just so I don't have to watch it go from a $100 game into a $200 game (I've already seen it go from a $30 or less game into near $100, ugh).
I'm sure there are many other old timers like me there that want certain titles and would rather pay now and hedge their bets instead of watching prices continue to go up, and it contributes to the inflation even more. Unfortunately there isn't much of a solution except to stop paying those prices for the games, but that only works if everyone does it, which is unlikely to happen, so prices keep going up.