Given the cost of molds and how many pieces they can produce, non production parts amaze me. (Production parts in other colors are reasonably boring, changing color isn’t expensive.)
I’d expect either non-production parts are made from less tolerant molds, or perhaps LEGO stores the molds for future use - I can’t see spending the amount a mold costs just to melt it down (unless some major structural problem were discovered). Heck, for some of these parts they could recover the cost of the mold by just selling the pieces directly.
Then again, maybe I’m off. Maybe a single piece in a single set requires many tens of molds, and so the cost of a one-off is not that high. Or maybe the non-production parts are from a bygone era.
Anyone able to measure the tolerances on the non-production parts?