$1 per game. All games priced at this level, however, should have DBVs/DBAs in the coin door ready to accept currency. While I don't think $1 per play is unfair (anymore), I do think it's asking a lot for the player to:
1. Approach the game to ascertain how much it is to play
2. Get out their dollar to play
3. Realize that they need to get the dollar changed into four quarters
4. Find a change machine to accomplish this
5. Return to the machine
6. Insert four quarters, one-at-a-time.
7. Hit start and play
If you want the $1 (which you do, or at least you should...), you need to do your part to make it as easy to spend/insert the dollar as possible. Fair is fair. Any machines which don't readily accept a DBV in the coin door can be the exception(s) to the rule, but in my view, they should be priced lower as a result.