What is better? To put 3 IRCs or 3 dollars in my envelope?

Hello! I am from Bulgaria and before 3 days I found this website! I didn't know about fanmail before. But now i love it! I have a few questions. I hope to get answer ASAP. - I want to send mails to USA. But how many IRC-s i have to put in the envelope? How can I calculate it? - Is IRCs working in US...