A couple of years back I had a pretty large sell-off on eBay, and I was doing free shipping, since I was getting REALLY great rates with FedEx.
But with the eBay costs going up, and getting a little burned a couple of times with flat rates and real far away destination....now I charge for it, but I'm still one of the more reasonable guys around.
Typical would be flat rates to anywhere in the CONUS, and I would do something like a piece of rack gear (figure under 20 lbs) for like $15-$20, depending on the items and it's cost/value.
I shipped a Traynor 100W head and a 412 cab (two packages) to Florida for like $125 total...and they were about 130lbs total.
I hate the guys who charge $15 for the item and want $35 to ship it.....or you have the ones who charge $100 for a guitar and $300 to ship it. The logic is, eBay doesn't collect on the shipping charge, so they devalue the item and then make up for with the shipping....more money in their pockets. In the end, it doesn't matter to the buyer I guess, if the guitar is really worth the $400 total, but I don't know how eBay doesn't clamp down on that...seeing how lately they try to control everything. You can't even send someone your direct email without some creative typing in their message system.