does anybody know how much the little crowns with the combs on them cost?
I just got back from Disney and paid $10 each for the little tiaras you're talking about. (Neither my friend or I got the hairdo that comes with the tiara, but we liked them, so we got them separately to wear some other time.)
Yup, my friend and I did BBB as adults. It was fun!!

I got the Pop style with the electric blue-colored extensions and the colorful Mickey head clips (you can buy those clips on their own in the store for $1 each, by the way). My friend got the Diva style with hair that matched her own and the crystal barettes/Bobby pins (I'm not sure which they are, as I never saw them after she took them off; I don't know how much these cost separately in the store as I didn't look for them).
The person who did my makeup did it way too heavy

but I did wear my hairstyle through the next night (washed it out the morning after that). It wasn't hard to wash out, either - I shampooed twice just to make sure it was all out, but I really don't think I needed the second shampoo.
It was a surprise for my friend and she'd never heard of BBB before that morning (when "Tinker Bell" left us a letter about it with pix from the brochure y'all posted - thanks for that!), so when she saw all the little girls doing it, she was a bit worried, LOL. I told her many adults do it and she felt much better when she saw another adult getting done after we were finished.
I definitely recommend it for adults!

I would do it again.
BTW - when you bring home those little crystal tiaras, make sure you bring them home in a closed bag! My tiara lost the top stone at some point, but I kept it in the small Disney shopping bag (with the handles tied together) they gave me for the purchase and the stone was in there, so I'll be able to fix it with some glue.