Server & Client, Who Sends Packets?

[luke14free]

Hello,
I'm working on a simple project for mobile phones, but because of traffic wap/web cost I would like to know one thing

If I have a server( A ) and a client( B ), and the client connects to the server I have something that could be drawn in a way like that
B-->A
Suppose that my server A is just an Ftp server, that reiceves packets from the client B. In this case, B is sending the files, and A is reiceving.

Now let's think that A is a mobile phone that has to pass to B a file of 50kbs. A has a cost foreach kb of 3 $cent (hypotesis). B will pay 50*0,03$ (=1,5$) but how much will A pay? I'm excluding all the FTP server messages as the welcome one and so on. Will A(the Server) pay 1,5 too or not?

Thank you,
luke14free