"eBay didn’t charge a fee on shipping and the last time I bought something, they didn’t charge me a fee on the tax."
- that is because the seller pays the fees to eBay, not the buyer, unless it is embedded in the "Buy it now" price by the seller.
"15% is the price of admission to their vast buying audience and site logistics." - "overall eBay charge 15-16 percent fees and tax every item I sold " - " the sad part people don’t understand how  eBay charges both ways seller and buyer seller pay fees and tax buyer pay only tax"
- don't know where you all are getting this information, eBay charges 13.25% selling fee.
"No real explanation, other than that"
- why would you think they owe you an explanation? One either uses their business or doesn't.