In my mind it comes down to simple free market forces.
A salesman has a job to do: sell a product for the best price possible, for his boss/business and himself.
A potential buyer has a job to do: acquire the product he needs at the best price he can. (and that's assuming you can be bothered always pushing for the lowest price!)
Somewhere in between is the price they'll possibly agree on based on how much the salesman knows about his product, what price range he's willing to show a little flexibility on...and what the market is willing to spend on various items etc
It's then up to the buyer to do his research and decide how badly he wants the product and how much he's willing to pay, based on similar market factors that the salesman has had to be aware of, and to put a value on the salesman's knowledge and advice.
At the end of the day, you can always buy a product somewhere else if you're not happy with what you are being offered as a deal.
I don't get too worked up if I can't 'talk' a salesman down to the price I
want to pay. If I think I was making a fair offer (based on extensive research) and the salesman doesn't go for it...then I'll buy somewhere else if I can find the item at that price. And have a little chuckle while doing so
But there also comes a time when I have to be willing to accept that the price they are offering is
fair. And that's based (again) on a lot of factors, none the least being the convenience of having the item in stock right there and then when I want it...
Shop around...do your research.
Just my 2c worth