The worst buyer's guilt I think I ever had was when my boyfriend and I took a trip to NYC and decided to check out the Discovery Museum when they had the Body Worlds: Pulse exhibit. It was an exhibit about anatomy and the displays were preserved human bodies, without skin, to showcase muscles and just basic anatomy and such.
I had reservations about going to see it because I'm really faint-hearted with that material, but my boyfriend really wanted to go and I was kinda curious. I paid $30 per ticket for us, so $60 total, went in, and couldn't make it past the first room without feeling light-headed, nauseous, and dizzy. My boyfriend walked me through the exhibit (it was a one-way thing...) and I had to wait in the gift shop while he went back and hurried through it. So, $60 down the drain as it made me feel sick to my stomach and he felt bad so he rushed through it. No refunds available, either.