Located a short ferry ride from the mainland town of Playa del Carmen, the island of Cozumel is a popular resort destination that is focused on diving and other water sports. It has its own small airport with direct flights from some cities, but most people fly into the much larger and nearby Cancun Airport, which has lower fares and far more direct connections.
Cozumel is considered part of the general Cancun resort area, which also includes the so-called Mayan Riviera that runs from Cancun south to Carrillo Puerto. There are nearly 100 hotels on the island of Cozumel to go along with about 400 more on the mainland, and all of that competition helps keep prices down for most of the year. The Christmas weeks are peak season and hotels charge quite a bit more then, while the summer rainy season is when room rates really get low.
As with the rest of the general area, prices for hotels and restaurants have a wide range, with 4-star luxury places starting at around US$250 per night in the low season, and simple guesthouses starting around $40. As long as you can get here, you should be able to enjoy yourself on any budget.