best I can figure on the sterling phenomenon is that its all based on emotion.
Sterling used to be the king of silver as you could do stuff with it, I like it, I can melt it directly into jewelry and its good to go.
I think it has a lot to do with Dealers shooting them selves in the foot by being lazy. Pushing either 90% or .999 fine. Dealing with .925 involves Math and thinking. With 90% traded at a face value X "X" say 12x and with Fine being at what ever price plus or minus X...these products are of a known weight and measure, and are common.
When you had old units of Measurement on sterling, or companies selling sterling at weird denominations say in Grains or pennyweights but made of sterling, say franklin mint crap. It was to help hide the bullion value in order to push a product at a premium...people would be .8 oz of fine silver for $19.95 in the early 70's...they were buying the packaging and not the $2 in silver.
Also most utility silver like flatware and tea pots and other things like jewelry are not standard units of measure. You have to weigh them, make a calculation, it takes time, it takes knowledge . Anyone with half a brain can figure it out. But again. the quick and easy factor is not there.
Take that and you get product pushers. Dealers who say this is better than that when its all the same. Why does every A hole out there want Englehard or American Eagles? cause there coin dealer had it or there gun dealer or grandpa said it was better just because...when in fact its the same stuff as generic mints put out. Why do people commonly accept generic silver rounds but when it comes to gold freak out?
Why did the Chinese Chop Mark all Spanish and American and other Silver coins of the era? they were interested in the metal, Not the maker....today people are about the maker and not the metal so much. A product of Western Marketing is all.
100 years ago...it did not matter, Sterling traded the same along with fine or coin or 90% or %80 or what ever it was. IT was all Good Silver. Fast Forward to today, Marketing has taken hold and yep...people want one thing over another...even though they are not using it, just storing it as wealth or on speculation...it should all be the same.
As a jeweler of course I like Sterling because I use it. I can turn it into other things, I dont have to alloy it or mess with it, its good to go...but in a day and age where people who use it for its utility is a vanishing thing. Stores of Wealth are of more interest...with the marketing.
Same thing about 14k Coins, Why do dealers shy from then? and 22k and .900 coins. All trade at discounts compared to Fine.
Krugerrands trade to me for less as they are just 90% I have to refine it to use it. Maple leaves I love to melt down. Cheap, numerous, Ready to alloy.
American Eagles are the only 90% gold coin that brings a premium....here.
I was in Germany a few weeks ago and stopped by a little gold shop. I was able to buy 1/10 oz American Eagle Gold coins AT SPOT because they could not sell that "Shit" in Germany. I bought em all and sold them back in the states at a $25 per coin profit. The going rate now.
So its all perspective, demand, and marketing...why are proof Eagles going for $1700 per oz right now? Home Shopping network is selling them for that. Marketing.