You can stay in a pretty good hotel on the beach for $100. When you consider that everyone on the island has the same view, the same beach and the same reef, lots of folks can be very comfortable with a lot less.
Our preference is condos...We very much like the Belizean Reef, The Palms and Coral Bay Villas. If you're willing to spend in the range of $100, take a very close look at Coral Bay Villas! Great value, beautiful place, excellent location!
Good luck!
Jim