If it is a newer KX60 you may find a cheap used, but not abused basket on the popular auction site. If older, good luck :-( And don't even think about buying one from a dealer unless you ABSOLUTELY need a new one.
I am facing the same dilemna with an '86 KX80 I just picked up for a friend's kid. Basket would have cost me over $125, so I just filed it. I didn't check the actual size of the wear marks, but .020 - .050 sounds about the same.
Worst case is that after another six months I need to replace the basket with another used one from that auction site, or maybe even buy a new one. But for now the grooves are gone, the clutch action is smooth, and the bike works...until he tears it up again ;-)
Good luck!