The travel industry in Mexico is very unfair to the workers who make it happen–the room cleaners, servers, drivers, etc. There are exceptions, but generally the Mexican resort model involves paying very little to local people.
To be sure the locals are glad to have jobs, but $5-10 per day just perpetuates a poverty model that grips our neighbors to the south.
I see this as wrong by any code of ethics. Mine is the Christ follower code and the great teacher clearly taught and lived that fairness in pay was a basic part of moral living.
So first of all we pay our guides a good daily wage–usually $90-110 USD per day. Beyond this they receive regular bonuses for work well done, large groups, etc.
We also equip our travelers to tip and give in such a way that people along the path of our trips receive funds that help make up for low wages.
Another way we pursue fairness is to use hotels, eateries, transport services that pay well. This is not always easy, but we make the effort.