It depends what you mean by expensive, and also depends on the weight of the envelope you're sending, and the size and weight of the envelope you're expecting to get back.

There are loads of threads on this board with postage prices, or check the Royal Mail website for outgoing mail and the USPS site for the return.

I've thought about the "writing-swapping" idea, but think it would probably be awkward with someone you didn't already have some sort of understanding and relationship with.

hi all, i love collecting autographs and i really want to start sendong to america but im out of work and dont have alot of money so was wondering if it was expensive to send to the u.s or not worth it at the moment?
i was also wondering if it would be easier for someone from america to get the autographs for me then send them over and i could do the same with uk autographs?
any suggestions?