Maybe I don't understand the role of the FBO at some airports in Mexico. I am flying down and have no practical experience flying into Mexico (hence my membership here). I plan on arriving at Mexicali, clearing customs, refueling (about 20 gallons in my RV-9A) and taking off for my second leg to MMLT, fueling there and departing, then spending 10 days in MMSL. When I contacted MMML, I got a response from Manny aviation services that list unbelievable fees to land, clear and fuel totaling just over $1400 including handling, communications fees, parking fees, $430 for the multi entry fee. Something doesn't seem right and I get the idea I was just corralled into using services I don't want. Am I allowed to land and just clear, refuel and depart? Do I have to use these services? How would I avoid them?
Thanks for the time and I look forward to some information.

"Once you have tasted flight you will forever walk the earth with your eyes turned skywards, for there you have been and there you will long to return" - Leonardo DaVinci