It is specifically against the rules for a seller to cancel all bids and end the auction early without a winner IF it is because s/he deliberately set the Starting Price lower than s/he was willing to sell for, and it hasn't reached that high. This is considered fee avoidance because eBay charges a substantial fee for sellers to have a Reserve Price so they aren't promising to sell as low as their Starting Price.
But there are legitimate reasons why a seller would have to do so, and a few years ago eBay got tired of having to divine the subjective intent of a seller who took that action, so it adopted some procedures that make it less attractive to do so with that intention: it can only be done before the countdown reaches 12 hours AND it charges a fee (the FVF% for that seller in that category times the highest cancelled bid--the hidden maximum, not the showing "current bid" amount) when s/he does so (with the first such fee per calendar year possibly waived to allow for the very occasional legitimate reason for doing so).
