I am both a buyer and a seller on eBay, however my response is as a buyer.
First there are products listed numerous ways such as
(1) Listed price (buy it now)
(2) Auction
(3) Price + Make offer
(4) Price + Free shipping
(5) Or combinations thereof...
If I find what I'm looking for and it's overpriced, I make a reasonable offer (and match the shipping)
There are times when I find something that's acceptably priced but the shipping is off the charts comparatively. I will ask that the shipping be reduced to match others (equal vendors). Many times the vendor will agree.
I buy a lot of automotive parts, both new and used, and shop for the best deal. I have no qualms about making an offer.
Many times the vendor will either agree or counter-offer. If the counter is reasonable, then I buy now.
What I have experienced is that a great many of the asking prices are purposely high and an offer is acceptable if the vendor wants to move his inventory and still make a profit.
FYI...recently I made a reasonable offer and was ignored...eBay sent me a memo apologizing for the vendors lack of response. A simple no or a counter offer would have been acceptable.
Rant and rave all you want, but understand that you are a part of the eBay community, and as such you need to understand how it functions and follow the rules of engagement. Being considerate by responding with a simple no would suffice.
Being a mature business person will prove beneficial in the end.