The Lufthansa one seems a bit like a scam to me. On my last LH booking, LH offered me fixed price upgrades and "bid for upgrade". The minimum you could select in "Bid for upgrade" was only marginal smaller than just paying for the upgrade straightaway.

The prices for both upgrade possibilities were more expensive than buying straightaway the higher class. No doubt that it will be interesting to those suffer under the Y only travel policies and are willing to pay out of their own pocket for a little more comfort, but traveling privately it doesn't necessarily make sense.