Unfortunately that "cost of doing business" is using a scam company like Paypal that strips sellers money so one ends up owning their job, rather than expanding it into the growth of their own business. Sellers use it because they fear the items they sell, won't turn a profit fast enough if they don't. Sellers that don't use it, are not necessarily greedy to avoid the fees, but do the selling for the fun of it, in which they already have the money and can afford not using a criminal organization such as Paypal.
There's no doubt in my mind the overall picture here is Ebay/Paypal trying to keep their sellers indebted as an addiction to use their system or crash into bankruptcy. Imagine if all the fees were returned that have been stolen, literally stolen by Ebay and Paypal, one would not need social security and that person could buy that car, that house, those stock investments. Cellars cleared out, Ebay has just duped another household, now empty.