Supply from strong hands is very low simply, because prices are not rising, nobody wants to sell something they know they can't replace.
A big glut of coins came out April-June time period due to gold sheet, many dealers called old customers and brought new supply to market which they had previously viewed as bullion. That was great time to buy or trade out for higher quality numismatic coins for many of us, I sold common date proof sets so I could own a few more 1/2s. Now most of the supply in the US is exhausted and it is hard to find much of anything in high quality (condition and rarity). There is tons of bullion coins floating around, but those have no buyers even at few percent over melt.
October-December mainland dealers subscribe to new coin issues, they have to prepay to secure orders, orders arrive in November-January, they sell and use the proceeds to buy back dated material January-April. It is a cycle that repeats itself over and over. The other challenge is between Thanksgiving and new years it is risky to ship in the US, packages seems to get lost due to high volume, so I typically sell very little during that time. I tell all my customers if they want to sell they must do it before Nov 15.
