It's in business to provide a profit to its stockholders. Would you expect management to do anything other than provide the maximum return to the owners? They are balancing per-unit cost and volume. If another company comes up with a less expensive way to present an auction to the same number of interested buyers at a lower cost, eBay will lose sellers. It's the way capitalism works.

In the interest of full disclosure, I'm not an eBay shareholder, although I have owned it in the past. I'm a frequent buyer and occasional seller.