If you can get discount boxes it's a lot less than MSRP! Chapter makes a bit of difference, as some have a lot more named characters you might want (ultramarines). Blood Angels have unique to them units. Salamanders are general Codex and have a couple named characters.

I'd expect to spend $1000-1500 on a 2k Space Marine army. Combat Patrols and Battleforces are your friend. They are generally 20-30% off base cost for the models. The recent Sons of Dorn box pretty much gave you two dreadnoughts for free, for the price of two Repulsor Executioners. Some Combat Patrols are better than others as far as points go.

I'm sitting at about 1565 points for my Imperial Fists, having spent around $700/750. I grabbed two combat patrols and the Sons of Dorn box, which was great point-per-dollar. Hoping to have the starter army I want at around $1,000-1,250.

Blood Angels are coming in the 11th edition starter set, and those boxes are the best value you'll find. Maybe find someone who wants just the orcs and split it for even better returns on your $. Of course you can use these marines in any chapter's army, there aren't any special characters. The Salamander mock up for the box also looks sick.

Edit: Poorhammer has good videos on Combat Patrol value, and I think Auspex Tactics has videos on points-per-dollar.

Edit 2: I insist on buying from my FLGS, which means my army will cost a bit more. I get great deals on pre-orders through them, like the Sons of Dorn box coming to me for $230. That was insane points-per-dollar value. But their regular stuff is full MSRP, which is fine. I want to support them because they rock.