People seem to forget that, at the time, cod4 on the PC had its fair share of obnoxious players. But it was easier to deal with them with admin privileges. Map packs also cost money now... more than for sheer profit... because these days they are much more complex to produce if you want them to look good. All the various internal tools needed are much more complicated. Some of them are proprietary belonging to other companies that want money. So it makes no business sense to give them away for free.
So while the packs may be overpriced, or maybe not, they are no longer going to be free. That can be a good thing tho. Now that they cost money we can expect and demand more out of them. If the maps suck we dont just say 'hey its free'. We complain, loudly. The in-game transaction idea with real world money, with the money going to the developer, is total profit however. So far they are only cosmetic in this franchise. You cant buy anything that actually increases your power. As it is now I dont see a change in that, with money for improved weapons, without backlash and affecting the player base.
Personally, Im bored with military FPS's. I think the FPS as we know it is a dying genre. Not without a major change that focuses on an actual global community in the style of WoW. Or an RPG. A single world filled with NPC's and dedicated squads (8 players max) not random teams. Attack and kill NPC's to get XP and items. Or... focus instead on going after other squads, killing them all, and stealing their items. Then sell them in-game for new equipment. As used items of course. Then again, if you lose, they steal yours. It promotes full squads among friends to avoid 8 on 1 battles. Unless, if you work alone, you are very very careful.
Certainly that is monthly fees. But if the game is big enough, and addictive enough, it could be more than enough to run all the infrastructure and make a tidy profit. Especially since such a game could last years. Not months. Oh and provide ways that players can do something to get the monthly fee waived. This is not for the casual 'hop on hop off' player.