Yea 55k is 80 bucks on here cod ghost not worth 80$ 25k to 35k would prob work a lot better for you and it will sell faster as we'll just my opinion :p
The problem with credits is it's subjective to opinion. If you buy them, than you are certainly correct in every way, but most people don't buy them and a lot of people go by the 1000 credits equals $1 opinion. I really set the Buy It Now based on what a lot of newer games are going for. Last week I had a new copy of Baman Origins (a $35-ish game) go for 37k. Like everything here though, the market will decide the price.
No problem. Some people do put them really high. I tried to put a fair price but maybe I was wrong. Most the time I don't even put a Get It Now price because it can be better to let tbe market determine the price.