I caught a couple of youtube clips where the value of the Joker is not always at €220,000, in fact, some of the Jokers were worth over €500,000, the over €500,000 episodes were the special "themed" episodes.

From this video at youtube:
http://www.youtube.com/watch?v=YCmwcqiF6IM

Joker being worth €550,000, in a special themed episode:


From this video at youtube:
http://www.youtube.com/watch?v=SlbrNltT6eA

Joker at only €180,000:


One of the €500,000 wins, with the joker being at €200,000:


Joker being worth a whopping €630,000, in a special themed episode:


I wonder what the highest amount has ever been for a Joker (overall amount and the multiplier), I presume the €10,000 multiplier is used on standard shows, whereas the special shows get higher multipliers.

Note, I noticed the Joker question (usually in general knowledge) is of low difficulty, yet some contestants still get it wrong!