Specialists make commission. For instance, if you buy a washer and dryer and they ask to get your name and number, they're saving that on their login to get commission.
The only negotiation they'll do is on clearance stuff.
They'll price match local competition, ala Home Depot, Wal Mart etc. It has to be the same brand and model, though. They'll take an additional 10% off of the competitor's price but be sure to check them up on that as the cashier may not know and may not change the price.
Also, I was just rereading this and realized it sounded thrown-off what I said. The 0%/12mths is if you have a Lowe's Credit Card, I just assumed that's what you were talking about.