While rare coins can indeed fetch high prices, the claim of a single Bicentennial Quarter being worth nearly $28 million USD seems exaggerated.
Such an astronomical value would be highly unusual for a single coin, even one as rare as a Bicentennial Quarter.
As for four more quarters worth over $750,000 each, it's possible that these are extremely rare or error coins that have sold for high prices at auctions or in private sales.
Some quarters, like those with specific mint errors or low mintage numbers, can indeed command high values among collectors and numismatists.
However, it's important to approach such claims with caution and verify information through reputable sources or expert opinions.
While rare coins can be valuable assets, their worth is determined by factors such as rarity, condition, demand, and market trends.