I think most people pay via Western Union or some other money remittance service.
I have a PK account - so I was able to mail a check.
As far as pictures and prices are concerned - check out this thread:
http://www.paklinks.com/gs/classified-ads/305526-some-of-my-work.html
Proto is one of the most transparent sellers on GupShup when it comes to detailing how much she charges.