There is a $145 round trip ticket price for Las Vegas to Cancun on Aeromexico through Expedia.com. Site shows 7 tickets remaining. Depart April 25 with April 29 return via one stop Mexico City.
Expedia ticket Aeromexico Airlines
Las Vegas LAS – Mexico City MEX – Cancun CUN – MEX – LAS
Could be a mistake fare, but perhaps not.
American and United Airlines have $252 round trip for Las Vegas to Cancun.
American Airlines Las Vegas LAS – Phoenix PHX – Cancun CUN – PHX – LAS