I was planning to go Cancun because it's insanely cheap, but now I hear the prices skyrocket during peak season?

So don't go during the peak season. Or stay in the Hotel Zone's hostel or in Ciudad Cancun on the mainland for $20 per night and take the bus to the HZ. It's hot (and sometimes wet) there during the summer anyway, but our weather in February was perfect.

We book our all inclusive vacations about eight months ahead through a chartered airline for the end of November into a couple of weeks in December. We get $1000 off for early booking, and the weather in Cancun is sunny and comfortably warm to hot. Prices are still reasonable at this time.

That's true In a lot of tourist destinations. Prices are lower in the offseason.

Yes, it is a shame that having some good simple fun can cost so much. Things are often more fun when you think you are getting a bargain.