eBay

"their fees should be based on sales price "

It is, the total sales price. What the buyer actually pays for the item and that includes taxes & shipping costs. It's the same as if you bought it from a store. For example: The retail price of the generator on the shelf has the shipping to the store, taxes paid, etc. built into the retail price on the sticker and (if you are a sales tax state) more tax. eBay is just a big store that shares it's info because it's participants are both buyers & sellers on the same venue.

BTW: The buyer does pay 13.25% of the added sales tax.

They charge 13.25% of whatever the complete total you pay for an item. I have sold on eBay since the beginning and have sold many thousands of items. Combining the approximate shipping cost to the furthest city away from me, factoring in box & packing helps me determine a Buy it Now price. Then I add 7% to the final cost to the buyer as I always offer free shipping. This way sharing the the eBay fees with the buyer and only pay about 7%. Selling on eBay might seem expensive, however the results, due to massive exposure, lead to quick, easy turnarounds. Then there are the easy shipping labels, checkouts, buyer & seller protection. I am now nearing the end of liquidating my record collection of over 700 album, only about 200 to go. To me it is not a rip off at all and an easy way to buy & sell online.

"They are making more money on the tax and shipping and they shouldn’t be charging me for it."

- maybe, but they are handling the funds and dispersing funds to the IRS, and the shipping companies to make it easier for buyers & sellers. That requires management and attention, therefor money. stereo5 is correct, maybe eBay is not for you.

"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.