I've never paid more than $25 to ship a long gun, and that's insured for full value. I use Fedex. I just shipped a sxs from CT to Alabama, 3 day for $16 plus change, insured.
That being said buyers need to look at the shipping price you advertise before bidding, or send an email requesting to negotiate on the price/shipping prior to bidding. Once they bid they have entered into a contract and should honor your price as you've stated it in the ad.
This is one reason I stopped selling things on Ebay, once they changed their feedback system to favor buyers it became skewed and unfair. The last few items I sold didn't go well and I had buyers who basically extorted partial refunds from me in exchange for positive feedback. After 250+ positive feedback scores and no negatives my last 5 sales had 3 buyers attempt this.
