I've just been to the Orange Bowl, a Holiday Inn on the beach, and the airport. I can tell you the hotel within the airport is incredibly expensive...fortunately for us...Delta footed the bill.
I'd go to the beach and eat oysters on the half shell.... 
That is pretty normal -- Airport Hotels are notoriously expensive. When I have been stranded, I bill it back to the company, so I don't care that much.
Anyone know how far it is from the airport to the beach? And what a reasonable cab fare would be? And where the midget wrestling ring is?
Delta cancelled out flight out of Key West and sent us and the couple we were with.....by cab....up to Miami, put us up in the hotel in the airport itself until our flight out the next morning. No windows....but a whole wall of mirrors

. We each got a $20 food voucher. It didn't pay for 2 drinks a piece!

We drove up from KW to the Orange Bowl and Holiday Inn told me they were 15 minutes from the stadium.....only if you were in a Bell helicopter. We were an hour! After the game the only place we found open was a Denny's. We went back to KW first thing the next morning....it was warmer there!
We used to have about a 3hr layover from Atlanta to KW in Ft Lauderdale and we would go to an oyster bar on the intercoastal. Only long enough to eat a couple dozen oysters and get back.
Traffic around Miami is horrendous. The rental car drop-off is a couple miles away from the airport. We avoid flying into Miami.