But, as an auction, KLM is not obliged to accept the highest bid. The highest bid is not the "price". The "price" is what KLM has decided internally is the minimum value they will accept - which in your scenario instead appears to be €219.

That the highest bid is so far off their target means that no-one will be upgraded via the bidding mechanism.

(I have seen the opposite, where I have been offered upgrades at check-in that were lower than where the bids had climbed to. Far more sensible, particularly when €259 gets you an upgrade on a transatlantic segment )