Why do so many sellers take offense to offers on their listings?

Just to add, as a Seller I have a set price(ad)and lowest I am willing to accept. If need be, to help my ad along, I will offer "free shipping" in asking price "only" inside my country. It also depends on what I'm selling, a cable is free, a 60 lb amp not so much. If I come down in price during negotiations shipping cost and insurance always plays into it. PayPal fees are always mentioned in the ad and will be charged to the Buyer at going rate, "unless" it is sent as friend/family which is free to the Buyer.

Last, negotiating is always part of the dance, and hopefully all parties leave the floor smiling and with each others phone numbers......

I don't understand it.  Buyers want a bargain and sellers want as much as they can get, generally.  So what?  As a seller, if you get lowball offers, just say no.  No reason to get offended by it. Buyers can't  be faulted for trying to get a bargain.

I do not think many sellers  take offense to offers,  just a vocal few...

@jl35 Its amazing the number of sellers you will find that are overly proud of their gear.

As Eric Idle says on Monty Python's The Life of Brian "ya got a haggle"