They are relatively cheap as a single unit, but when you get 2 @ $159usd each, they become expensive. I gotta say they are beautifully manufactured, very tight tolerances, some of my eyepieces actually wont fit without a fair degree of force, however one can get an adapter to overcome this. It is mentioned in the information at Adirondack that the tolerances are very tight, which is a good thing I reckon. Also Televue are coming out with something similar but it is incorporated in a diagonal. Aries from the Ukraine have produced them and Roland from Televue is working out all the sales details. I emailed the guy from Aries, cant think of his name off hand (Valery, or something like that) and he said they would probably be significantly more expensive than the Adirondack version. Interesting stuff. Oh yeah, the PADC got an excellent write up in the June S&T , US version. This made me go for the sale.
I just found out that these can be obtained from a guy here in Adelaide (Matthew Lovell) of:
http://www.telescopes-astronomy.com.au
apparently he deals directly with Adirondack. His prices I have found in the past have usually been very competative with what one can get them for in the US. An example is his price for the Losmandy G11 with Gemini, about $500 cheaper than anyone else here in Aust.