eh, yes and no. the cross bars, weather mats and cargo covers cost them almost nothing. if they are willing to start throwing in new tires or more expensive items, yeah you maybe left some money on the table.
when you have a price all decided that's a good price, before you sign, say that you will sign if they can throw in those things. Per the pricing thread, I was below average pricing and they threw in the weather mat and cargo cover. (I had assumed the cross bars were standard so I didn't negotiate for those)
and that wasn't even for a vehicle they had on the lot, that was in network they had to ship from another dealership a few hours away