It seems other artists are also seeing the benefits of Sidestep: Jared Leto was among the latest round of investors who helped raise $1.7 million in new funding.

For musicians, touring and merchandise sales are becoming increasingly lucrative as profit from record sales continues to diminish in the wake of streaming. An app like Sidestep allows Beyoncé and her contemporaries to target a market of fans who wouldn’t otherwise buy merchandise at gigs because of long queues at stalls.

This is a very practical idea, but how much will the merchandise be marked up to cover the cost? 

Likely a lot.

The site seems well-organized and clean. Offers more than simply purchasing from your concert seat, including buying in advance, after the concert, and having merchandise delivered. Basic prices are reasonable, though I have nothing to compare them to.

Could there be much of a hacking problem, from thousands of people gathered close together, spending money on one app and at relatively the same time?

http://sidestepapp.com

There could be a hacking problem if it becomes popular.

Without popularity it's probably not worthwhile to hack. 

It could get very popular. Right now, merchandise is available from these performers – e.g. two Adele coffee mugs are based at $20.

That's cool though I'm not sure how big the market for Adele coffee mugs is.