or only dollars above the wholesale cost
What makes you think there is only one wholesale cost?
At one point in my retail life, I was selling BBQs in a small shop that had three employees.
We got a better wholesale price than The Bay (a major Canadian department store that owns the US chain Lord & Taylor) on our BBQs because we bought a truckload at a time and about four truckloads during the very short Canadian season.
The Bay bought a dozen for each of their stores, which meant the trucker made six stops for The Bay and one for us.
In the same way, your competitors may have better rates from their shippers.
All sellers are aware of Paypal's discounts on shipping labels.
UPS and other couriers have lower rates for high volume customers.
I also have a better deal on postage because I use postage stamps, purchased at a huge discount when we buy philatelic estates. That discount is big enough for me to offer discounted (Canadian) mint postage here on eBay.
On eBay, I have always allowed 20% of my customer payment for fees. These include listing (including the 50 free listings or the lower cost Store* listings), Paypal, and here in Canada a 5% tax on the fees. This also covers my cost for Cookie Jar Insurance, self-insurance against transactions that go bad.
The number is too high, but that leaves me happy at the end of the month when fees are lower than I expected. Smoke and mirrors.
*They are no more free than Free Shipping is free. The cost of Store listings in covered by the monthly Store fee.
