I missed a few replies here...
Articsteve, Saturn cars' prices were generally lower than their competition because while the rest of the competition built in negotiation margins in the prices, Saturn didn't. So the MSRP was lower than similar cars. So if Saturn screwed people by overpricing, then everybody else is even worse in that regard.
You're the first I heard who said anything about trade-ins being valued less in Saturn dealers than in other dealers.
As for the idea that businesses will fail if the salesmen aren't paid by commission, sorry, I don't follow you that way at all. Salesmen who work by commission often become very aggressive and pushy, thinking this helps their sales, but some people are turned off by that. Whether or not it actually is successful or not is a complex question. An example of a successful no-commission environment is Best Buy which has become the biggest electronics retailer in the North-Eastern US while having no commission for their employees in sales, something that set them apart from their competitors.
Saturn's own ultimate failure is due to opposition to Saturn from GM's own bureaucracy and the UAW. Saturn started very well, in its first years, despite not selling any car to fleets (to my knowledge), the S-series sometimes sold more than the Civic and the Corolla. However, no investment on products was forthcoming from GM until nearly 10 years after its introduction, at which time it had become a way for GM to introduce new, uncertain technologies as tests in the real world: the 3.0L V6 in the L-Series, the infamous VTi transmission in the Vue and ION, the Aisin-sourced 5-speed in the ION, the mild hybrid drivetrain in the Vue and Aura, testing the direct importation of european cars with the Astra, and releasing cars to work out the kinks before releasing very similar products in other divisions (ex: the ION before the Cobalt, both sharing engine, platform and transmissions, the Aura before the Malibu, again same platform, engines and transmissions).
Saturn had become a real world laboratory for GM, which weakened the surprisingly strong fanbase it had considering the kind of cars it made (compacts). When GM ran into difficulties and decided to rationalize its brands, Saturn got chopped, its brand had become confused and dull.