Marketplace doesn't technically allow tickets sales due to the risk of fraud. Are they selling it through some other category to get around that (or maybe it's changed)? When I looked for concert tickets on there the groups were all scams.

I sell KSL tickets to BYU games all the time. Most people don't even bat an eye and send me the money (and I am trustworthy and send them the tickets). But if they are hesitant I offer to have them pay for one ticket then send them the one first. I would meet up if they came to a spot in the city I live.