"through hardening" or Flame Hardening, requires a different grade of steel, and a couple more steps to complete.... Case hardening is cheaper and quicker in large lots.... plus, case hardening only hardens the surface about 2-3 thousandths deep(at the most!)... this leaves the inner material of the part more ductile, which reduces fracturing.

there are other hardening techniques available.... look it up... ;-) and i'd bet the cheapo cones are not hardened one bit, other than a black oxide coating.

as to the original post... i've run into many hubs through the years that had larger balls in them... bad move! in all but a couple cases, the cones had been totally ruined as the balls contacted the cone at THE VERY SMALLEST EDGE of the cone... remember that fracturing i mentioned above? yep... the lip shattered, filling the grease with bits of really hard metal... the entire hub and axle set will be ruined if used for very long... BMX riders do this most often... along with not putting ANY GREASE in their bearings at times... seriously... NO GREASE!!!???!!! some stupid rumors run amok..... sigh... i hate lacing 48 spoke BMX wheels...