Well, the inline monitor would cost more like $1,000 USD installed in the US, and importing to Cozumel has challenges and costs; just being reasonable with expectations.
However, inline monitors are very rare south of the US. They shouldn't be, but insurance companies don't require them there as no one is going to sue - too costly and too little chance of getting much. As always: when you leave the US, you leave the US. :biggrin:
There just hasn't been much demand for quality assurance among divers. Most agencies and DAN have done little with the risk, and it's common to think that if the DM is happy diving the air - then it must be ok, false that that is. News of previous incidents and deaths around the Caribbean and Latin America have been suppressed as bad for business so the problem has long been overlooked. Today, it's still not that popular of an idea but it needs to be addressed.