Well alot of the progress in BIS' series are the from the ideas and work of the modding community. ARMA 2 borrows heavily from user made mods to ARMA. Those guys arent getting paid squat. Plus I play ARMA/2 for single player so constant new material wouldnt benefit me.
If BIS offered like a dynamic multiplayer world where factions fight and gain/lose territory, players gain rank (like gaining levels), choose a niche (aircraft, vehicle, infantry, command). And BIS maintained all this, provided the servers, provided the context for battles. And did it elegantly and bug free, that might be worth a modest ($5/month) membership fee. But as an option.