The thing about carbon is, regardless of what it's used for, is it's only as strong as its weakest link. That's why the nice stuff is expensive, because it's reliable. If you had a product that was comparable to another.. would you sell it at 1/5 the price? I'm not saying that every good deal out there for a low-priced carbon stem is going to fail, all I'm saying is if you find some killer deal on a carbon stem that is 1/5 the price of other comparable products there is probably a good reason for that.

Chances are these products are going to be fine. But in that slight chance it has any defects or is ill-produced.. based on Murphey's Law.. it's going to hurt.