Additional SEPM Costs?

Hi,

Firstly this is a non-technical question but could not locate the answer trolling through the forums.

Currently I have two SEPM's in my organisation replicating the same embedded database. Due to expansion I'm now wanting to add a further two SEPM's to make four replication partners. I understand from a techical perspective this is feasibly however, is there any additional cost to my organisation? My instinct tells me there isn't any extra costs involved but I just wanted to ask the question to be sure.

Thank you in advance.