As originally spotted by Eurogamer, trying to create a weapon you don't have enough resources for causes the below screen to pop up, which offers you the ability to get some additional parts through "downloadable content".
The game's associate producer Yara Khoury told the site that "You can buy resources with real money, but scavenger bots can also give you the currency that you can use on the marketplace. So you don't have to spend [real world] dollars."
She also refuted the suggestion that you'd be able to buy all the game's best weapons right out of the blocks, making missions a breeze. "No you can't!" she explained. "There are a lot of weapon parts that are only available to buy later in the game. Unless you're playing through it again [on New Game Plus]."
Pricing for the extra resources hasn't been revealed, but Khoury explained that different sized packs will be available for varying costs.
While this is the first game in the series to feature microtransactions, EA has published other titles that use the system. The most prominent of these is last year's Mass Effect 3, which allowed you buy reinforcement packs when playing the game's multiplayer modes