In the context of, let's say, Sweden, there are some men who will always want to pay for sex, so they'll either find a way in Sweden or they'll travel abroad. However, for the average guy, say myself, if prostitution was legal, it'd be very easy to hop out to a brothel. But if I have to get on a plane, fly to another country, come home, and then explain the bill to my wife, there's a higher bar set.
Again, we're never going to deal with all of it, but let's tackle the 80:20, the college bachelor parties. I met a guy who every Christmas takes his son to Cuba on a sex vacation, and that's their father-son bonding time. We can deal with that. If it's illegal, they wouldn't be going there. I'd love to traffic-proof every nation on earth, and I think criminalizing demand, going after demand, will deal with a large part of that.