Just about a year ago a friend told me of an acquaintance who needed to move some silver quickly due to a family emergency. Three 100-oz. bars, serial numbered, with assay certificates, well known US producer. Market value at the time was just over $15 per oz, so I was looking at about $4500 total fair market value. Asked the man what he would take, he first said $4000, then went down to $3600 for immediate sale ($12 per oz). It took me about 4 months to find a buyer with the market just over $16 per oz, at which time I sold for $15.50 ($4650 total with me paying $48 for insured delivery via FedEx).
What I learned: (1) 100-oz bars are much more difficult to liquidate than smaller pieces; (2) very few knowledgeable folks routinely pay spot (or premium over spot) prices, with lots of folks looking for bargains; (3) don't invest in such things with an expectation of quick and easy liquidity.
For most "investors in precious metals" I would suggest that a little premium over spot value is to be expected at purchase, a little discount against spot is to be expected upon sale, and such investments should be looked at only as long-term rather than quick-turn.
I made a thousand bucks, but it took several months and required some effort. Your experiences may vary.