I've shot some, they're just about as good as anything else.
I've got the Yugo M24/47 which was a transitional model between the k98 and m48 or so I've been told, someone bent the bolt and installed yugo scope mounts on it and put a butt pad on it. Fit and finish is great, and shoots stupidly accurately.
Are they worth $500? No, simply because they're not K98's. Would I pay... $450+/- with or without shipping for an in the cosmo gun with all the accessories? I'd be sorely tempted, especially for one hand picked. I suspect while quality varied, it wasn't anything to the degree as the japanese ww2 rifles where the first ones were amazing and the last ones were actually hazardous to shoot.