It's technically not duty free after you exit customs but there is a shop that sells alcohol. Not sure on prices
There is a small duty free shop after customs, before luggage, in the new terminal (Terminal 4), but it's really more for small gifts, not for bulk alcohol. If you're looking for something to bring to the resort for your room, you can ask your transfer/taxi to stop on the way to the resort, or walk across the street from the resort, down to your left, there is a pharmacy/shop that has a decent selection for reasonable prices.
Several years back I did a comparison on vodka prices comparing my PA liquor store to duty free at the philly airport to duty free at the Cancun airport to Walmart to across the street from TTR. Here is how it played out surprisingly... Pa liquor store < Philly duty free airport < Cancun Walmart < Cancun duty free airport < across the street from TTR. So the Cancun airport was not a good deal. It depends where you live of course but for me I now use wine bottle protectors and take bottles my vodka bottles protected in them in our checked luggage. If this isn’t about price and is about convenience then sure Cancun airport works
