How much is the SMS communication fee between peer-to-peer networks?

It is the short message transmission between mobile and mobile, which belongs to family "communication"; China Mobile sends short messages to China Unicom and PHS, which is not an intra-network short message (but an inter-network short message). Inter-network users have to pay extra, because they are not "family" with China Mobile. Hehe ~ ~, I wonder if you understand my explanation? thank you