I know I am late in answering, but I don't see why someone would ask a girl to go somewhere for that amount of money if they weren't serious, so the girl would know his intentions. But if there were some rich guy that wanted to whisk me away for a cool trip, hell yeah I'd go, and I'd expect to get some ass.
It all depends on how well I knew him and if I was attracted to him-I wouldnt have any expectations except that I was going to the Carribbean for a weekend of fun in the sun. I would sleep with him only if I wanted too and it depends on how long I knew him