Quote from Marksman
You do NOT want to use this method, as you lose 15% from selling the gems and another 15% for the transfer to PayPal.
The best way to transfer B.net funds to PayPal funds is to obtain a trusted friend who also plays Diablo III and has a connected PayPal account, presumably someone you know in real life. You then get your friend to post any bad item ($1 fee) on the RMAH for the amount you want to transfer out of B.net funds. Your friend must indicate that the sale will be sent to his PayPal account (15% fee). After the money is in his PayPal account, he can freely transfer the money to your PayPal account.
Using this method, you will receive ([funds to transfer from B.net to paypal] - $1) * .85 dollars in your PayPal account.
This is probably a better way to do it indeed. But not everyone have trusted friends and want to go trough this method.
This method is just an easy way to do it if you dont want to include anyone else