Ross parts are like anything else: what the market will bear, or whatever you think is fair.
If we're talking about Mark III nose-caps or complete unissued woodwork, this can be very pricey stuff. On the other hand, I have seen brand-new bolt-heads go for $2, although that was some years ago. (Came in very handy, too!)
Best thing you can do is list whatever you have and either set a price or ask for bids. Best way likely is to set a price. You'll soon find out if it's too high (I'll be crying in my soup, loud enough that you won't need a telephone!).
Good luck!
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