No doubt there's going to be some low-hanging fruit (speaking relative to the experience of the participants) that is going to get scooped up quickly, so why would they open the program at something higher? Just high enough to entice the experts to pick off the "easy" ones seems the intelligent thing to do.
When they go a year or two with no bugs found maybe you'll see them start upping the bid.
When they go a year or two with no bugs found maybe you'll see them start upping the bid.