Howdy. Yep. Definitely in agreement. I haven't spotted anything relating to gold or silver in my books as yet, but since you pointed it out, I will keep looking. Yet, payment of some kind was always relatively prominent in many quests - one can understand the average team taking a bar of gold over something else.
As for the correct answers / knowledge situation - well.. maybe it's not unfair, but what I'd bicker about is why they were the only team of the series (I suppose I'm wrong, but even if I am, they were amongst the minority) to answer 2 correctly and earn no more clues. All I'd argue is why is wasn't kept the same for everybody - even if it appears blantantly obvious, by adventurers code or otherwise, which objects to take.
Yeh, I'm still a bit baffled by the door-monster idea. I'd imagine, as you say, the 'requirements' on each level are more difficult - but it was still far easier having 50 / 50 chances along the way than having to answer two of Merlin's riddles, and then a real stinker of a level 3 riddle to have a chance of winning in S3. (My op. anyhow. )