Depending on the context of the sentence, this normally means that you have bought or obtained something expensive. For example, "My brother is having twins. Oh wow, well he can kiss his wallet goodbye!" Or, "My friend just bought a 1980's Jaguar. Really, he can kiss his wallet goodbye."

It means to be prepared to lose your money. It is often used as a warning that the listener should reconsider a purchase/offer/situation that will likely end with them losing their money.

It means that you will spend a lot of money. It is usually used in a case where it is considered that you are wasting your money, but sometimes, it just means you are spending a lot. "I want to get the latest tablet, with all the latest apps!" "You'd better kiss your wallet goodbye, in that case."

Ники, а почему ты поставил мою фотографию к себе? Нехорошо.