Do those toning shoes really work to burn more calories??

I see those "toning" shoes everywhere. I cannot believe that people will pay anywhere from $85-250 for these shoes! Hard to plunk that much money down for a pair of shoes that you are really not sure about?
These shoes have a rocker bottom, which is curved from heel to toe. The idea is that the shoes are designed to induce instability, with the idea that the body will use the core and intrinsic muscle contractions to help strengthen and burn calories. Different website claim up to 15% more calories burned. Well, lets see where the source of these studies are... the companies themselves! Of course they will tout more calories burned!
Speaking to physical therapists and back specialist, they liken it to walking on a mattress... very cushiony, but very unstable. They have reported an increase in knee and lower back pain with these shoes, and our office has seen an increase in achilles tendon pain and tendonitis. This makes sense... with a rocker bottom, you are essentially hyperextending the achilles tendon which inserts behind your heel with every step you take.
So buyer beware... and then you can judge yourself if these shoes "really work." It may be just a fashion statement... and not a very attractive one at that.