I generally think of what I'd like to recieve for an item and then add on £2 for postage and fees, and give a total price, sometimes it works out better for me, sometimes for the buyer, you choose when buying an item whether to pay the total price, including the fees, ulitmately that is your descion. What a person asks for their item is their choice, whether that be including or excluding fees.
Do you not think when someone lists something on ebay they think well I will lose x amount on fees so I will put the BIN price up by x amount, and even shops, I'm sure they bump up their prices to allow for fees too, just because you don't see the extra because it isn't seperate from the price of the item doesn't mean it hasn't already been added into the total.
It's not really an unreasonable request and no one is forcing anyone to buy anything. Also people often negotiate on price anyway meaning they end up with less then they had first hoped, and while you may think it's unfair, do you think it's fair on someone selling something to have to cover the fees when it's really the buyer than gets all the protection