Believe me, we have looked at all the options. I used to be a pilot for Delta and Northwest Airlines, so I know about every trick to get from one place to another. I can't travel Saturday to Saturday this trip. United is the only airline that goes to Cozumel same day right now, and only on Saturday. My wife is a nurse and works blocks of days on, and then has a block off. It rarely lines up to get a Saturday to a Saturday, so we aren't able to take advantage of that.
The 45 minute layover is a problem as well. We tried to take the direct flight once 3 years ago and we had to deice leaving Great Falls, and missed the connection. Then we had to scramble to get on the Cancun flight, arrange shuttle to playa, take the ferry, etc. Living in Montana you have to accept that you don't have all the flight options of the big cities. We have not taken the charter flight previously, but factoring in the lost wages from 2 days of work, extra hotels, etc., the $450 cost is much cheaper in the end. Of course, it is likely we will be canceling our trip now so we may not get to try the charter this time.