Most dealers try and resolve matters in-house. They are independent. Unless, they are part of a group.
A car dealer isn't going to call around to OTHER dealers for some accessory.
And then there is always the matter of what pricing you offer another dealer (sometimes competitor). Some simply offer retail pricing. Hey, you want it or don't you? So now what? Do you mark that up and sell it to your customer?
The CC company has to get your 2% from somewhere and take a percentage for themselves. There are many CC transaction companies all with differing "discount rates" and differing terms for the business. 5% is one of the really high ones, but it is that high because of your 2% rebate card. The CC transaction company I am familiar with charges a different discount rate on every card. We don't know what the cut will be until the end of month statement.
These are good posts.
I will add, what appears simple, from a buyer痴 perspective, is often not and it痴 the salesperson痴 job to shield you from those challenges and keep things simple.