I would not get hung up on it. For a fixed priced classified or an auction, just build in the 3% if it bothers you so much. For a "or best offer" advert: if they offer a certain $$ amount and paypal payment, then that is their "best offer". Take it or counter offer.
PayPal Surcharge
I have noticed alot of people add a (3% or so) PayPal fee to their items and I wonder if everyone is aware, that is against the user agreement. It seems that PayPal looks at sellers as "merchants". This is cut from the Paypal website:
-No Surcharges. Under Visa, MasterCard, Discover and American Express regulations and the laws of several states, including California, merchants may not charge a fee to the buyer for accepting credit card payments (often called a "surcharge"). You agree that you will not impose a surcharge or any other fee for accepting PayPal as payment. This restriction does not prevent you from imposing a handling fee in connection with the sale of goods or services, as long as the handling fee does not operate as a surcharge (in other words, the handling fee for transactions paid through PayPal may not be higher than the handling fee for transactions paid through other payment methods). Nor does this restriction apply to Pound-denominated transactions by sellers residing in the United Kingdom listing items for sale on a UK-based website.
-No Surcharges. Under Visa, MasterCard, Discover and American Express regulations and the laws of several states, including California, merchants may not charge a fee to the buyer for accepting credit card payments (often called a "surcharge"). You agree that you will not impose a surcharge or any other fee for accepting PayPal as payment. This restriction does not prevent you from imposing a handling fee in connection with the sale of goods or services, as long as the handling fee does not operate as a surcharge (in other words, the handling fee for transactions paid through PayPal may not be higher than the handling fee for transactions paid through other payment methods). Nor does this restriction apply to Pound-denominated transactions by sellers residing in the United Kingdom listing items for sale on a UK-based website.