Recap is wrong...

They originally paid $30 for the room. Since the Tropicana gave the chippers a $5 discount because of the convention rate, they only had to pay $25 in total... which divides out to a net cost $8.33 per chipper.

They paid $10 each and should have received $1.67 back but only got $1.00. Take .67 times 3 chippers and you end up with $2.00 that the bellboy took.