OEM software (and hardware) sounds cheap but it's actually illegal to sell and buy.
It also usually comes without manuals and may well be a stripped down version.
OEM software is licensed for distribution with specific hardware to a hardware manufacturer. Standalone distribution is strictly against the license agreement (usually the CDs will tell you this, lines like "for distribution only with XXXXX").
What happens a lot though is that stores will rip open the hardware boxes and sell everything in them separate for a total price that's more than what they could have sold the complete package for.
For example, a highend videocard with your software example might sell for $650.
Sell the card as an OEM card for $550 and the software for $200 and you're $100 ahead...
Respectable stores won't go for this and allow purchase of OEM components only as part of a package deal with other things it can be sold with (so OEM videocards would only be sold when you also buy most or all of the other parts for a PC).