My one, and only experience, was that the amount you pay them is a fraction of the TCO.
1) This is THEIR trip, not yours!
2) They are always hungry! We were going to the beach and she said she was hungry. I said we would get some food to go and she REFUSED to lower herself to take-out food. She wanted to go to an expensive sit-down restaurant and shook her head in refusal to accept less. I went on to the beach with no food and by God there was a sit-down bar that served food. She runs over there and orders a feast.
3) They are always thirsty! They want the fanciest cocktails.
4) Now is a great time for that tattoo the've always wanted. I walked away and the tattoo man stop talking to her.
5) OOOps, where did she go? She's ducked into some store and found something to buy her.
6) They hate the A/C because they don't have it at their house. 80 degrees is the lowest acceptable room temperature.
7) They love the TV!!! They can watch it all night and some do. They DON'T want to talk to you.
A) They will pick the channel for you.

It is hard to get rid of them after you return.
9) During the trip, you will be reminded of everyone's birthday or other gift-giving occasion that's coming-up.
10) If she sees a friend or your buddy brought another girl, they will gab so much that you won't get to talk
11) They love to play Bob Marley at full volume the whole trip.
12) They like to smoke the same crap Bob smokedł.
Basically, you are there to fund THEIR party. If you think you will just tell them off and put them in their place, just remember they have unlimited emotional endurance and can out go 200 round in the verbal octogon