In a nutshell: Supply and demand.
In the case of bands like Keel, their stuff has been out of print for years, therefore copies of their albums are hard to come by on the legitimate market. Thus the ones that do become available are expensive.
The counterfeit/bootleg version of "popular" CDs are due to unscrupulous douchebags scamming unwary buyers into paying big $$ for what they think is an "original" issue.
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"If you're a false, don't entry, because you'll be burned and died!"