Ibiza! There was 20 of us, and even though they say it's really expensive when you're in a big group the drink offers make it insanely cheap! Big clubs are expensive, we went for a week in San Antonio but they've got a strip of clubs as well as the superclubs and imo the smaller ones were just as good and generally free entry. In the big clubs you can expect to pay around £12 for a vodka redbull...but we predrank in bars before we went and got offers like 3 triples, 2 spirit and mixers, 2 shots each plus 3 bottle of champagne to share between us for 8 euros.
We did 7 nights all inclusive for around £385 plus around £250 spending money. Some of our group spent as little as £200 spending money and some of the lads spent £700+. It depends how much you drink when you're out plus what you're doing during the day ... plus we had to pay for some unscheduled medical treatment for one of our friends :/
But go for it!! It's definitely the best out of the three and there is no need for it to be expensive!