We go in and out of Cancun (MMUN) several times a month. We do not use handlers there. Generally it costs us about $1000 to $1200 including fuel for the Lear 25 everytime we go there. That includes fees, tips, etc. The tourist board doesn't let the airport slip too much. Be sure you have your mexican insurance, a letter of permission from the aircraft owner and if 135 have mexican permits.
They have a new Commandante there now and he is feeling his oats a little.