IMO, the value of abalone handled knives will go UP. Because the resource is not being replenished at the same rate of harvest in the wild and farm raised abalone are not big enough to have all the colors when they are harvested.
California supplied everyone until 1997 and IMO, there will never be another commercial fishery in California. As for the Paua, (New Zealand) 70% to 80% depending on the source, is either poached abalone or undersized. Only 20% (approximately) is legally taken. Obviously at some time that fishery will have to close also.
Tasmania - Australia, Tasmania suplies 25% of the worlds abalone, mainly to China. These are the Blacklip Abalone and Greenlip Abalone. Sport harvest allows 10 per day.

No Surprise, that fishery is in danger too!
Many species are not suitable for knives (out of about 130 species). One which would look nice is the pinto abalone off Brittish Columbia, Alaska, and the San Juan Islands. But the shell is way to thin. They have a few all the way down to California, I found one about 80 ft deep off Fort Bragg. Man, that is deep for cold water.

No Scuba gear is allowed in California - Free dive only. It's breath hold, kinda like snokeling - only DEEP!