Hopefully your experience can keep others from making the same mistake. I'm not really surprised; there are many establishments that rip off tourists and hope they don't notice. Book at a private beach club for one price and places with good reviews. May be a little more expensive but not so much in the long run and you will have a better day. Maya Chan always gets good recommendations. We went to Almaplena (a little farther away) and they pay for taxi to get there. It's a small place, very quiet, includes food and drinks - a great experience.