The extra .50 is a hassle by itself - do you have a change machine easily accessible at the location? Seems like you might lose some casual players who just want to use a spare single bill to play a game. Do the experiment and see how your take compares to your current average, might lose some plays.
Seems to me like a game of pinball at $1 and 3 for $2 is is still about right. Godzilla will be worth more when paid off or paid down and sold to recoup costs, so it's a bit of a wash imo.