I too have to laugh at what a discussion this thread has generated. I simply wanted to give the heads up that the rates were going up. Yes, 20% seems excessive at one time, but the rates have not increased in 5 years, so this is a proportionate increase considering gas prices have increased by 100% in the last five years!
Those of you up in arms about a few extra pesos make me go hmmmm. Really? In the grand scheme of your expensive vacation, it's nothing! And if you don't like it - you have the choice to walk or rent a car - or you could always buy your own car to keep down here (that was sarcasm BTW)!
But the direction a handful of you have taken this tells me you must not have anything more important to worry about - or maybe you do if a few extra pesos over the course of your vacation are causing you this much grief. In that case, maybe you can't afford to be going on vacation at all, like most of us here on the island, including those "should be millionaire" taxi drivers

Yeh, I know, we're "always on vacation."
Relax and enjoy your Cozumel vacation! The choice is yours or not to use the taxi service
By the way, the weather is gorgeous down here - you should book your tickets soon if you haven't already