It can run you a pretty penny (just like everything else onboard) if you're not careful, but there's so many great things to get it's hard to keep track sometimes! We actually didn't know about the items sold onboard, so we actually picked up our items at the Pirates of the Caribbean gift shop at Magic Kingdom before we sailed. There's actually a much bigger selection of pirate merchandise there, but the prices are pretty much the same from what I remember. We did not see anything sell out completely, but I think it was because either there were some people who did not know what the party was all about or did not care to spend any extra money on them. However, we did see a few people with pirate accessories, so it would be safe to say that there were some who brough their own instead.