Hm, I haven't tried that yet, but I think it is possible. It usually works very well in specialized and non-chain stores. If you cannot find a salesperson with any decision power it might be harder.

You can try asking the next time you buy something big. The worst that can happen is them saying no, if you really asked nicely.

PS: I dented a rental car and got a huge bill. I called them up and basically said 'discount please?' They gave me a 20% discount, and that was without any kind of arguing or confrontational talk, just the question. So it's not just for stores.