From the episodes I've seen, the box was either a klunk or was worth considerably more than the cash award envelope.
Couple of questions:
1. Was there ever a package in the box that was worth less than the cash award envelope but wasn't specifically a klunk? (For example, giving up $2,000 in cash to find a $1,500 prize)
2. Does anyone roughly know the prize/klunk distribution? I was guessing 5 out of the 30 were klunks, but I could be wrong.