OSHA-approved clear wraparounds; whatever was cheap at the distributor that day, pretty much always under $10.
I have gone the "expensive" eyewear route before. They get lost, crushed in the shooting bag, scuffed up and all kinfds of other nastiness. In the real "tactical" world, when they fog (and fogging, despite all of the "fixes" that people have developed, is often unavoidable), you ditch them and pick them up later, if someone else on the Team didn't step on them or if they didn't land in the omni-present dog doo or other bits of biological nastiness that seem to be common in "tactical" settings. You also need to be able to ditch them quickly if it is time to transition to a pro-mask or NV systems. I usually have a couple sets in my range bag, a couple in my helmet in the trunk of my car, and a couple in my locker on the van, so I always have some available. I also made it a point (when I was responsible for such things) to keep several pairs in the load plan on the van.
Ballistic eyewear protection, in my experience, is basically a "disposable" item and should be purchased and treated accordingly. Buy something OSHA-rated for ballitic protection (I think it is the "V50" standard, but don't quote me), but buy cheap.