I'm guessing the studios get a kickback in return for retailer exclusivity on said catalog titles. It's not permanent -- usually 3-6 months, sometimes longer, sometimes less -- and the only thing I can figure is that the studios' "bonus" for entering into a retailer exclusivity agreement overrides how much $$ they'd make from a national retailer release. Because we're talking about catalog titles, i.e. HEAVY METAL, OVERBOARD, etc., not titles that would sell in mass numbers.
Meanwhile, the retailers like it because it drives up traffic for those type of titles.
especially when titles are only available from someplace like Best Buy
I'm no fan of Best Buy either, but they sell lots of media titles, and they're everywhere, and for most of the country it's not hard to find one.
To be honest, the pricing has nothing to do with Best Buy either, the studio sets it. HEAVY METAL is $15 this week, and that would be perfectly reasonable for a Day One catalog title at Amazon or elsewhere.
