eBay's listing fees mean you pay more to list an item with a higher starting price. Simply put, it costs the seller more to have $100 auctions than $1 auctions. Same thing with reserve auctions, the seller pays for the privilege.

In a very real sense, eBay is encouraging shill bidders with their listing fees. They'd be gone overnight if listing fees were the same irrespective of the auction start value. After all, eBay is still getting their ending value fees.