Couple of years back I did an over the bars at Innerleithen and landed eye-first onto a pointy rock.
I was wearing some Oakley Minutes and all they had was a small scratch from the dead centre of the rim to the edge of the frame where the rock slid across. There was enough force in there to “pop” the skin on my nose open where the (rounded) frames dug in.
Scars on knees etc. I can deal with, but when it comes to eyes I would rather pay out for decent kit (from genuine sources).
I’ve still got those glasses, though after about 10 years of riding in all conditions the fire coating is coming off. I snapped the frames once in really cold weather and Oakley sent me some new ones for £7. I’ve now got some flak jackets with black polarised lenses, mostly for driving (you can’t see sh1t in the woods with them on) and for making blue skies look cool. But I’ll probably get some clears or grey lenses for biking (CRC were doing them for £40 and they just snap in).