And there's a reason why LEGALLY BLONDE was never made available for sale.... it costs a ton of more money for retail/direct-to-consumer distribution than to just have MTV pay you a fee to broadcast it on their channel. In this case, the producers of LEGALLY BLONDE, which likely covered some (or most) of the filming production expenses, are guaranteed a set amount of money from Viacom for the broadcasting rights. It's likely that the producers would then be privy to additional fees if certain ratings benchmarks were achieved. Those numbers are, however, never made public.
With respect to SHREK, many people are forgetting that this is a franchise propped up by Dreamworks Studio. They are a major animation picture company and have more to gain in the longterm by investing in the creation of a high-definition video recording. It's more likely than not that on a very basic level, they lost hundreds of thousands of dollars on their video recording. But it's safe to assume that Dreamworks saw it as an important, longterm investment. That was the accepted "price" of increasing exposure for its film/merchandise franchise to a larger audience.