I use OEM ( probably wrongly) to mean a part that is made, that is like what came in a bike when it was new. MK3 had the PTFE thrust washers, not plastic ones. Some real NOS ( new old stock) pre MK3 iso parts surfaces I have are very rough in the finish and would wear the thrust washers like a random orbital sander.No, it isn't a cost thing. What does OEM mean?