Earny Money Back App
Yeap there is app to get back your money back, which is Earny.
Earny app works very simple. First you need to download Earny app from itunes and link your email and Amazon Account.
Now, Earny app will check your order and try to find lower price than your purchase price.
If there is a lower price than your purchase price, it will request from your bank (with minus 25 percent of company cut).