Have a search through the forum there's literally hundreds of posts on money etc. As a rule of thumb though I always say a grand a week and thats enough to get wasted every night and go 3 or 4 clubs. But as the chap above said, you can spend as much or as little as you want, it all depends on how mad you wanna go. In my last trip I spent £1700 in 8 days and had no money the last two days I was there. But that was really going at it every night.
I've noticed though since my first visit in 2006 and my last visit in 2011 that Ibiza is actually becoming even more expensive, partly due to the $h1t exchange rate but also because even some of the smaller bars now like itica, ibiza rocks bar etc are charging 12euros for spirits and mixers. If you wanna have a cheap night now you haven't really got much alternative other than to get a bottle of vodka from the shop and get hammered in your room / on the beach
