For those of you out there who own a pair of MDR-V6/MDR-7506 and are curious about changing out the ear cushions...I may have found an alternative in the Koss R200 replacement ear cushion. They are cloth over foam and pretty comfortable. They are only 5 dollars and postage was like a buck.
I don't actually own the V6, but Jeff Guidry I think said that the UR40 and the V6 cushions look almost identical. Then the UR40 cushions look identical to my R100s, so by the transitive property of headphone earpads they should fit.
Anyway, the total cost would be like 6 bucks so I figure someone would like to try it out.