I was queing for a match, while simultaneously looking at the customization menu. I had 600 credits. I remember that my mouse was over "Black and Blue tracksuit pants" for the insurgent when I entered the match. I hadn't clicked on it or anything though.
Once I came back from the match, I noticed my character was wearing those exact pants, and my 600 credits were gone. All I had left were the 100 I had gotten from leveling up. I went into the customization menu, and changed my pants. I had the black and white track top, so it didn't look right. Then I went to look at the "Black track pants" section, just to see if it really bought it.
Surprisingly, I didn't even own it. It was still locked. So it took 600 credits from me, and I don't even have the item.
I was planning on buying the black fingerless gloves after I completed that match, but I guess I'll just have to level up 5 more times before I can do so. This is a bit frustrating, especially since I had quite a few more items I wanted to buy before credits no longer became too much of a goal for me.
Back to Co-op with target-snapping AI and a 5% chance of getting a team which will actually be capable of winning.