One reason why Warhawk has fewer reported retail sales is because the game is also being distributed on the PSN at a cheaper price, impossible to track for tracking companies.
I think it's pretty safe to assume that 30% of buyers decide to pick downloadable version up (according to surveys) . It would give around 140k as for week one. Solid as for multiplayer only game.
I'm sure Sony makes a lot more money on downloads - I wouldn't be surprised if they earn twice as much as for retailer version.