Triple P, I agree that as the risk is rung out, the price goes up. It makes perfect sense to me as a student of economics- less risk, higher price. But I do know what can wind up with nothing by trying to gamble on outcome. The beta ( risk reward calculation) is very poor on hot tosai. They cost 10 times more than tateshita but can crash and burn just as easily. I think buying three year olds is buying value for the money.
But I don't think koi are appreciating assets either, as a student of economics! Truth be told, once a consumer buys a fish he or she is very fortunate if a koi holds it's value as they all tend to depreciate in time. The name of the game is to have a long run of enjoyment before the decline. I'm not sure I ever knew a hobbyist that sold a fish for more than they paid? I have a very good friend in the hobby that paid 4.5 million yen for a super tategoi prospect and now, after five years of growing fees, can't seem to sell this 36 incher for even 2 million yen? Most of us are happy if we can recoup 50% of the purchase price for high class fish.
So once again, to answer your question in 300000 words or less

---- I think a breeder or dealer can have a fish appreciate on the front end, but there is no secondary market for 'used' fish so I doubt that a fish can be bought for 10M and sold later for 30M by a hobbyist. The one exception is IF the seller is willing to add money to buy a new, more expensive fish and then the dealer will broker the old fish to make a second sale.
Sorry don't know enough about the line you referenced to comment or add anything that you probably already don't know. JR