I imagine that's a conservative figure, but I'm sure someone will review them and put them to the test. If a sub-5mph crash is going to damage them they aren't very sturdy, that's for sure. If they were able to handle moderate abuse it would make the price tag seem more reasonable.
That being said, I can see where someone who wants to do a lot of indoor tripod-mode flying would want something like this. These guards really add a great deal of protection that would keep the props from damaging walls/furniture/etc, which is the main reason I have never attempted indoor flight.