I went to three shows, and spent $100 for the first two, and $150 at the the third. Each time, I decided before going what would be reasonable to spend and took that much in cash with me. Yes, I did have my credit and debit cards with me, but I did not even think once of using them.
BTW, having "just that much cash" can help in a bargain. It happened twice to me :
Seller : "I'll let it go for $xxx."
Me : "Would you take $xxx-$75 ?"
Seller : "I'll take $xxx-$30."
Me, opening wide my wallet so that the seller can see I'm taking everything out : "I have $xxx-$75."
Seller, after 10 seconds of silence, starring at the wallet and the bills : "ok, for you I'll let it go for $xxx-$75"

Of course it's the whole game, and the seller would have let it go, but it could have taken a few more minutes. Both time were just a few minutes before the show close. Helps a lot too.
Betty, the entrance is usually around $10.