Those sets come from the golden years of overproduction. There were multiple companies producing way too many cards, and some of them even tried to hoodwink collectors by intentionally printing "error" cards. Take the Score hockey cards - they printed sets in English and in French, and more than enough of each version to satisfy the genuine collecting market many times over. Dealers bought cases of them and still have cases of them (this also coincided with the rise in "card dealers," something we never had in the 1960s). It was an artificially inflated market, and it has not recovered since.

You can check eBay, but I think the other valuations are probably right. They will likely cost more to ship than the cards cost. Beckett's is fine for "star" card values, but even at 1 or 2 cents apiece for common players it dreams of an active market that just isn't there anymore.