It's always some impatient idiot that ruins it for everyone. We've seen it happen on this board. I saw it happen in real time to US Dragon Slayer on the Turbo. Just one idiot.
The inflation started with an increase in popularity and interest. Then outsiders get a whiff of potential profit and start influencing the market. There are people right now whose source of income is trolling the places where people used to get good deals, getting those deals, and then reselling at eBay prices.
Even Goodwill (which is NOT a charity, but a for-profit business) is opening up a brick and mortar video game store, charging eBay prices for games that people donated to the not-charity FOR FREE. That makes me beyond angry.
First thing that has to happen for the bubble to burst is interest has to drop. I see new people talking about the hobby every day, so that hasn't happened yet. The ridiculous prices will help in bringing that around, though. Once resellers aren't making enough money to continue to do what they do, they'll dump their stock and move on to the next fad. That'll bring prices down. At that point, all the fly-by-nighters will get rid of their games while they still have some value, and the rest of us can go back to normal.
Actually rare games will probably remain expensive, though.