There's a word for what you witnessed: spiff
Sales people can earn more money from manufacturer incentives than they do in salary or commission from their employer. In some cases the payment for selling an item can exceed the profit the store makes on the sale!
Apple has never paid spiffs so salespeople go out of their way to push other products instead.
Best Buy sales people are not on commission that I am aware of.
The one word you are looking for is probably not spiff, it's ignorance.
I've heard it all from the woefully ignorant BB sales force including these gems;
1. You can put a PCI video card in an iMac.
2. Blu-Ray players suck because they don't play DVDs.
3. Macs are MORE susceptible to viruses than PCs since PCs come with virus software pre-installed (along with a ton of other bloatware).
MS has gotten into the act too. They have put together training materials for Best Buy employees that tries to teach them that Windows 7 PCs are far better than Macs for a number of reasons including this darling;
"Mac OS X forces customers to learn a new and unfamiliar operating environment".