Originally Posted by ermis177

There is no way you will get a PE to C as low as 200 dollars even if the plane is empty. The bid price usually tends to be a bit lower around 100 dollars.

Originally Posted by oliver2002

The bid price minimum never changes. The fixed price upgrade varies with the availability of the lower booking classes in the cabin you want to be in. Closer to the departure the availability vanishes, so the fixed price will go up. At 72h you will no longer see cheap fixed price upgrades since P will be zeroed out, unless the C cabin is very very empty.