You're right Casey. Also, here's a little trick. The boys X large size i've found is akin to a men's medium. For example, i ordered the boys X large for the Polartec Air Core 200 wt fleece, hoody jacket, and it fits my wife very well. My wife is a bit under 5' 10" with large breasts and curvy body and strong frame.
So i'm guessing the 9.99 boy's X large down vest should be similar and be able to fit at least a medium. Also, if you read the reviews, some mention that the vests run a bit large anyways.
The boys 9.99 and the men's 14.99 vests otherwise look very similar. I don't have much spending money right now, but i'm pretty tempted by the 9.99 deal!