The things we will buy with real-world money are fancy paint jobs, hula girls, Ryan Steiner bobbleheads (BOOM, headshot), fuzzy dice, C-bills which can be earned in-game, etc. They have explicitly stated that real money will NOT purchase a gameplay advantage that cannot be bought using in-game money.
Example of what you CAN do with real money, according to the devs: Buy a polka-dot paintjob, fuzzy dice, an 8-track player, and some flaming skull stickers for your Atlas. You can also buy a wad of C-bills, which you can earn in-game anyway; some people don't have the time to grind all the cash up, as they have both school AND work, so they can buy C-bills to help make up for that. Also, you can purchase a temporary account upgrade that increases your xp and C-bill production.
Example of what you CANNOT do with real money, per devs: Purchase a non-stop orbital bombardment that glasses the half of the city your opponents are starting on. Purchase an RAC/20 for your Atlas. Purchase Hardened Reflective Reactive Stealth armor, which takes half damage, reflects lasers, deflects AC/missile shots, and is hard to see.
Also, I don't think the devs will allow real money to purchase combustible lemon munitions for missiles/autocannons, as those would be pretty overpowered.
Edited by Aethon, 01 June 2012 - 11:27 PM.