I've been dinged on feedback for my seller fees, and I charge my cost, refund any excess, and don't charge for "handling" or materials. I decided I need to offer more shipping options, including some cheaper ones, but that's a hassle in itself, and can result in exposing items to problems en route. Not long ago, I shipped a wheelset, carefully packed in a wheelbox, via Parcel Post at the buyer's request. All the documentation was correct. A month later, the box arrived with one wheel missing and apparently no sign of damage or pilfering - though you can be darn sure it was messed with. If I recall correctly, I wound up refunding the full amount. Buyers can't always see things from the seller's perspective if they don't sell themselves, though I perfectly well understand the problem of seller's using shipping as a profit center. But there's a simple solution - get the shipping cost before bidding and don't bid if it's too high. The problem takes care of itself that way. Buyers sometimes treat eBay transactions like they're buying from a retailer instead of someone with a wife, a job, and a 3-year-old.
Here ends the sermon.