I have been selling on Ebay for over 5 years. but only just started using AUCTIVA. Like yourself, I don't overcharge for posting Just 50p or £1.00 to cover packing etc. There appears to be a trend these days( To get around paying Ebay fees) To charge extortionate fees for posting and a nominal fee for the item. That way the seller isn't bothered if it only sells for the minimum amount, as he is making his money on the postage costs With No fee to Ebay.
I think it's about time someone else started another Auction site to rival Ebay. They have a Monopoly and therefore can charge what they like, Listing Fees, Sellers Fees, Fees for using Paypal. Thats why I only accept paypal from people outside of the U.K.