Demand has certainly increased dramatically. The choice pieces have always been few in number - a fraction of a percent, and they have always been able to find a home. Over the years a good number of these have found their way into museum collections, either as bequests or as direct purchases. Museums were particularly active in the second half of the last century, though funds are somewhat restricted today. Bequests such as those of Weightman and Clarke-Thornhill ensured that the BM had a significant increase in the collection, with the latter allowing them to take any coin for which they previously did not have an example of the die. Thousands went to them as a result. Similarly the Fitzwilliam benefited from the Henderson bequest (1933) - an act which eliminated a LOT of high grade material from the collector scene as he only collected choice pieces. Blackburn Museum's collection was essentially donated by Hart in 1945. Again, a significant number of rarities were removed from circulation. In the past, dealers such as Baldwins would have bought the book, i.e. any unsolds would have been acquired by them at reserve (if any) or at bargain prices. This was ok as it meant that they could build up stocks and keep a glut from saturating the market. The extent to which this happened was clear when Baldwins were taken over and the basement cleared. Many rarities which had been off the market for maybe 70 or 80 years suddenly became available again. However, since WW2, this cushion has fallen by the wayside as more people had disposable income and populations increased, providing a broader collector base meaning that demand for lesser pieces increased. Today the collector base is much broader and those with deep pockets far more numerous than in the past. All of this creates a perfect storm leading to rocketing prices.