Muchas Gracia, Seņor Frugal, for your trip report. I'm glad to hear about this property; been considering a trip their myself.

Regarding your two "complaints":
Internet access and gasoline are two commodities that everyone pays a premium for in Mexico. I doubt they were gouging you, they're just passing on some of the significantly higher costs. Meanwhile, labor costs are dirt cheap, so they can afford to pay someone to someone to stand by your side and hand you a new towel every 20 minutes. While stateside, labor costs are likely to be on of the biggest expenses for an HGI, while internet access costs are just a drop in the bucket.

And as for gas, everyone pays the same price for gas from state controlled PEMEX, the only oil company. Though Mexican gas jockeys have been known to gouge tourists by "starting" the pumping without resetting the pump to zero. You may have caught someone doing this, but I doubt it -- US$20 for a half a tank sounds about right.