Google Play Credit

[Matthias]

It said I had $1 credit for until the end of the day so I bought a skin but it still took $1.50!

[MadMikael]

It said I had $1 credit for until the end of the day so I bought a skin but it still took $1.50!

Prices on Google Play depend on where in the world you live.
For example, a skin here costs $1.69... I believe it's cheaper in the U.S. and more expensive in parts of Europe.
You should always double check a price before you buy... I think it's standard with Google Play purchases that they list both the current credit (i.e. I used a prepaid gift card), and the remaining balance you would owe for such a purchase (and it gives you the option to choose your payment method - all in one screen.)

For Google Play purchases, you should get a receipt in your gmail, which lists total price etc. as well as a code that is a long number starting with GPA. Double check that and see if the prices are out of order.
If there is a billing error (i.e. they charged the incorrect price), it sounds to me it is likely at the Google Play end; if that's the case you'll need to contact them.
However, if there was an actual game issue, like you typed your account name wrong and the purchase was not received, you could contact an admin with that receipt code, your account name, and details of your issue.

For more help, check out the FAQ - section 4 deals with this sort of stuff.
viewtopic.php?f=25&t=14031

[Leone]

Do currency exchange rate fluctuations affect this as well?

[MadMikael]

Do currency exchange rate fluctuations affect this as well?

I'm sure it's possible.
As far as I understand it, the game developer sets a generic price, and Google Play adjusts that price for each market, which would be based on exchange rates and taxes as applicable.
If you're really curious, I suggest you check out the Google Play FAQs - there are those written for the end user (like you and me) and those written for developers (or potential developers) who wish to sell products on their store. Both types are publicly viewable; also, they have different FAQs for different regions, as well as TOSs (for example, the TOS here in Canada is different than the one for the U.S. or other parts of the world).