Like Ron, I can find nothing on the eBay site about PayPal being the only allowable payment choice come October. True, they changed their policy in March of this year to require that sellers offer PayPal or a credit card as accepted forms of payment, but didn't preclude sellers from offering other payment alternatives as well. Of course, if you can't run your own credit card acceptance system (and I understand these are quite hard to get, especially for small businesses), then PayPal becomes your only electronic payment option.
As far as double-dipping, if you have a physical business, you pay for rent and/or upkeep of the physical plant above and beyond the cost of your goods. If you accept credit cards, you pay another fee to the card issuer for handling the financial transaction. If your bank happens to own the property at which you do business as well as providing you with your credit card acceptance system, does that make them double-dippers? And, if so, are not the charges they assess on you fair and customary charges for doing business (assuming they are in line with such charges elsewhere)?
It seems to me one has a choice: If the alternatives eBay has given you are unpalatable to you, then you may choose to sell elsewhere. Otherwise, you may just have to suck it up and realize these fees are part of doing business on eBay. The only real vote you have on eBay is with your dollars. If eBay is truly instituting a policy as kat outlined and they end up losing significantly because of it, you can bet they'll be reversing themselves.
On my part, I'm somewhat with Matt R - I look for merchants who offer PayPal, although I'm not the purist that he is. If I find something I want bad enough and can get it at the right price, I'll use other payment options if needs be. My history with PayPal, which goes back to their very beginnings, has been an entirely satisfactory one, even when I had to use their dispute process for one purchase.