Um that's not really true. Sure pvp requires more Balance passes, but pve play requires more content. Player driven content doesn't cost anything to make and it makes up most of pvp games.
It does to implement though.
Yes - I don't think you're onto a winner there Jordan!
The single most expensive thing in ED by several astronomical units surely has to be the networking and other aspects related to real time multiplaying - which in over one and half years since alpha is still not working satisfactorily for many.
Then followed by endless PVP nerf and buff cycles and goodness know what else.