PAPA is only officially open to the public during the two major tourneys held there each year: PAPA World Championships and the Pinburgh Match Play championships.
If you go during those times, and don't care to play in a tournament, there is no fee to enter. All games are on token play. Prices as stated earlier by another post.
For non-tournament play, you'll find a greater selection of pins available during PAPA World Champs than during Pinburgh, because Pinburgh uses over 200 pins set up for tourney play that are off limits.
It's worth every penny of a trip you'd make there, even if only for a day.