It is a very simple tool, but it does the job perfectly.
I have this to keep an ukulele on place. Not that it's hard to play while standing without one of these, but sometimes you need to use your hands to grab a drink or whatever, and you don't want to lay the uku around.
I honestly wouldn't use this to hold a classic guitar or anything heavier than a ukulele, as it looks like it could get very uncomfortable very quickly, but for smaller instruments it is great.
It isn't expensive at all, but I think it should be closer to 5eu than 6.