I've rented on in Nassau many, many years ago and I can't remember what I paid but in general the condition of most scooters on the Caribbean islands aren't the best. Usually the tires are getting bald, the brakes pull unevenly & the steering is racked from numerous crashes. So check over the bike very carefully before leaving the shop/stand and make note of any existing damage.
I always take many photo's of ALL damage so they can't claim that you've did it when returning. Sometimes I'll take 20 or 30 photo's - close up's & all angles.
All that being said, there are more scenic islands besides Nassau to rent a bike as there isn't much to see on that island anyway but it is a fun way to tour if only to go to some of the beaches.