Where are you flying from ?
My recent travels to Darwin saw me ex PER on a saver fare and the upgrade me min bid was $190 and my ex DRW flight was down to Brisbane and the upgrade me min bid was $290.
As they were on 737s I let both go. But there were spare seats in the J cabin on both flights so assume the bid would have been accepted.
I use upgrade me bids a bit. Granted I often fly the long skinny routes rather than the busy SYd - MEL run but my only ever minimum bids have never not been accepted.
So start with the minimum.