I don't know, 8% for Paypal is not such a big deal in my opinion. If somebody needs PayPal funds quickly, I can see somebody paying 8% on the top of the price. Don't forget that we are talking about PayPal after all. There is 180 days window to chargeback. That's a huge risk in my opinion. Anything can happen in 6 months.
The more people who charge 10% (Or in this https://bitcointalksearch.org/topic/m.12661833 case 20%) the price of BTC will keep dropping.
That and the more desperate the scammers will get for their fix as less and less users (bad analogy I know, but still) will trade here for increasingly small transactions.
I understand what you mean, but all I tried to say is that considering the risk people take for accepting PayPal (and the risk is huge indeed), 8% is not such a huge mark-up in my opinion.
Of course 20% is just over exaggeration!
I have used a known exchanger on here and other forums for the past 5 months. They know I would not do a charge back. I have bought multiple currencies from them for my paypal. They do not charge more than 8% on all the transactions that we have completed. And actually, the more transactions we complete, the rate slightly decreases everytime.