That's actually very common, especially in states where you only have to pay for what you eat, so restaurants are all to happy to replace your meal if you don't like it.
That being said, I understand why you are doing it the way you're doing it, thanks to your explanation. As for the price, I don't think it's the price that people would balk at, but rather, the principle - the fact that they can flat out lose their money based on someone else's whim.
I think that if you figure out how to give them something for their money when a date falls through, then it would just make people feel better. I don't know what that could be though, so I'll leave it to you.
While I'm here, I'll add my vote to get rid of the Facebook requirement. I'm very single and ready to mingle, but I don't do social media.