OK here's my Privy opinion! Privies have been used this year to obstensively get around the 300k and 500k mintage limits of the 1oz Lunar Dragon and 2012 1oz Kookaburra respectively.
For the 2012 coins, the privy makes them less valuable than a non-privy version of the same coin.
In other years however, privies can make a coin more valuable. Take the 2005 Kookaburra for example. I have the Zodiac Privy Kookaburras of that year.
That is, each of the 1oz Kookaburras have a privy of Aries, Scorpio, Cancer etc etc making 12 in total, one for each star sign.
The 2005 signs of the Zodiac Kookaburra coins are worth more than a non-privy 2005 Kookaburra. Their mintage was also very low, 5,000 for each star sign I believe.
Also other Kookaburra privies have significantly higher value than the non-privy of that year. Examples are 1997 Gold Dragon Privy (mintage 10,000), 1996, 97, 98 European Union Privy (mintage 5,000 each country), 2000 Zodiac Privy (5,000 mintage each coin), Various 1997 foreign currency gold privies (mintage 2,500 each).
So, some privy kookaburras are certainly more valuable BUT were minted in much smaller numbers than the 2012 200,000 quantity and often formed part of a set.
The 2012 dragon kookaburra not only has a mintage more than 100 times more than other privy coins but it also does not form part of a set.