I went $10 over budget today doing a lunch shop at CF. Ended up ordering full dinners. With tip $17 over.
I bought a $25 gift card in December and got free cheesecake coupons, so I already had that on top of my $40 gift card from the last shop there. I even put the tip on the gift cards. The gift card did not take 30 days to arrive either. It was delivered in less than two weeks.
You can easily keep using the gift card for the next shop, so you only pay once. You can also stay under budget and save credit from a lunch shop to cover the most expensive dinners on the next shop.
I'll do it at least once a month if I can get it.