Hahaha I've so been there before!... Wifey is always saying that...

I recommend first looking for deals to JA then compare your awesome deal to the worst flight/deal you can find for his location. Point out all the money you could be saving... Point out everything horrible that you possibly muster up about their location. (Mexico is too dangerous, the conversion rate in EU is horrible, Costa Rica is too long of a flight, etc.)

I also make empty promises that "sure we'll go there maybe next year"... That might buy you some time. Of course you have to trickle in trips to their wanted destinations, occasionally. But that's later, much later

last technique used... Just pay for everything. It's hard to say no to going to jamrock when it's 100% paid for.

I hope this helps, good luck!