Here are a few more data points
I bid for economy comfort from economy
EWR=KEF- $110x2 ( I think this was $10 over the minimum) I did not expect to get it because there were only 2 economy comfort seats but the bid was accepted and we got Saga seats without the service.
KEF-SEA- $125 accepted. This was the minimum bid but there were quite a few seats vacant and I(just me on this flight) once again got a Saga seat.
I think this was a great bargain because the free coach food and lounge access saved me from having to buy airport food and the seats were a big upgrade over 3 in a row coach.