You can create a market for this bet at Fairlay.
In return you get 1 % of all fees generated by the market.
However, you would probably have to seed both sides of the bet
with some liquidity in order to get the market started.
I believe there is not this matter they concern about. What is the point to make this bet and gambling for it? More over the point here is about the acceptance bitcoin on their site which mean if they adopted bitcoin to amazon, I believe people wont sell their coin again and price will be stable and more of them are going to buy things through bitcoin and price will increase again