Good question.
You'd have to imagine that revenue maximising algorithms at the back-end would probably continually fiddle around with minimum bid amounts dependent upon amount of bidding interest ... then again, to do this might 'give away' too much information to bidders.
In any event, if there is a lot of bidding activity on any given flight I'd have thought that those in the low range would have increasing smaller chances of being successful, unless everyone is bidding the minimum amount - which then leads us back to .. would revenue management increase minimum bids as a way to push bidding higher than it normally would be if everyone just bid minimum and sat there?
I promised myself I'd have a look at this stuff a while back but never seem to have a moment to explore it ... does the system allow you to come back in later and revise your bid or is it a once only proposition?