I would quit the hobby if the prices were mostly all in the $300 range. I won't go over $250, in fact. And even $250 is a rarity (only three times thus far). The reality is that there are superstars at $200 and at $220 right now, so I see no point in contributing/encouraging the inflation. The other fact is that there are mediocre providers at higher (and based on what some have reported, much higher) price points. Based upon my experience, there is only a small correlation between price and the appearance and/or service of the SP.
As others have also mentioned, ultimately the prices will be determined by what the market will bear. If Jalimon is correct about 2018 being slow, we may already be witnessing the effects of the increase from $200 to $220 that the major agencies made last year.
I believe that an agency could, in the current environment, capitalise by lowering the price back to $200, at least temporarily.