The US$50 fee is the renewal fee (per month) if visitors want to extend their tourist card after 30 days.
Exit tax by international air is US$35 or US$18.75 by land. By water you just pay the conservation fee US$3.75. Air exit taxes are now included in most international air tickets so tourists don't really squeal about the pinch, since there are so many air fees and taxes, especially from the U.S.
There's no entrance fee, except if you need a visa (citizens of the U.S., Canada, U.K., EU and most Caricom countries don't need a visa). Visitors from Thailand, Sri Lanka, the People's Republic of Chin, Indian and a few other countries pay a whopping US$2,000 fee for a single-entry visa! I don't understand that.