Want to pay for dedicated Minecraft server hosting, not sure how much RAM to order?

Paying a dedicated server host, but not sure how much RAM (on the server) I will need to run FTB Infinity for… 10 people. (Average will be about 3-6 people on, 10 would be the highest max ever)

I keep seeing 512mb/person for a FTB server (4GB total) recommended. Am I completely misunderstanding what they are talking about? Cause a 4GB server is like $80 a month.

Don't play Minecraft