I just don't believe the whole melting thing. Why would anyone melt these and similar coins, when they're just as or more liquid as is, and have the added benefit of possible numismatic value the longer you hold them? I do like modern commems (as is), many sell for way over melt and many sell for around melt. Usually, the close to melt ones are the higher mintage ones, with problems (low grade) that inhibit future numismatic value.
It would depend on who's buying it and for what reason. Some places may only pay scrap from some of these and as such, they are treated the same as other scrap metal, usually jewelry. Provident is currently buying common $5 gold for less than melt. I'd imagine non-coin dealer buyers pay even less. The rate at which that happens would depend on demand for products containing a given metal and the cost of digging fresh supplies out of the ground vs recycling old coins and jewelry.