I have a bunch of those kits, too, for a future samurai diorama.
The ones you see on eBay at an asking price around a hundred bucks, have probably been on eBay at that price for many years, they're just not moving. $20 apiece is not a bad asking price and should move them pretty well.
They are pretty good kits and can be used to make some very nice display of medieval Japan.
If I remember correctly, Tamiya also made some 1/35 samurai, which can be used with the Aoshima figures, too.
The Aoshima kits are a good example of the variation in quality across the catalog. Those are some nicely-sculpted figures. The 1/72 WWII fighter kits that Aoshima put out, on the other hand, are pretty lousy, even in their day. Thick plastic, both colored and the transparencies, rough details. And their contributions to the Waterline series of kits along, with Hasegawa, Tamiya and Fujimi, fall somewhere in between.
Prost!
Brad