Technically, Mythics drove down the price of non-mythic rares, by making people open more product. The game is just really popular, and played by a lot of people with more money than sense. Also, people like me drive up the cost of cards because the market will bear it. I'm solely on MTGO now, but there are certainly a lot of profiteers in paper.Mythics and the price of the game in general has managed to keep me clean for years now. My schtick was always going to a few FNMs, scoping out the field, and building janky rogue stuff on the cheap with dollar rares and the like based on whatever was popular at the time. With mythics the way they are though my bread and butter dollar rares are typically now all 5-10$ minimum due to mythic rarity and I just don't care enough to drop any real-ish cash on the game.
I do so miss the look on the faces of the resident temporarily embarrassed pro players though when their full foiled faerie decks lost to my shitty mono green list packing maindeck squall lines and cloudthreshers.