Dealers in Antarctic Postal History
I buy a lot of material on eBay. eBay sets the standard for material in this field. Dealers can be put into two price catagories, well over priced, and good prices. Because of the dominance of eBay in this area, the best estimate of of the value of an item is what it will go for on eBay. Anything under $10 is essentially of nominal value and highly available. The dealers I recommend understand the availability of the material and sell at fair prices. There is another type of dealer which actively participates in present day antarctic activity. If you want contemporary material these are the people.
I've worked closely with a dealer in Christchurch New Zealand for a number of years. Working with quite a few key people in the Antarctic community, and his excellent location at the kicking off point to Antarctica for many programmes, he has some of the best contemporary material available, including some South Pole material that the two of us collaborate on. I have bought some very nice and desirable historical items from Steven at his list, and reasonable, price. I highly recommend Shades Stamps, Christchurch, NZ. Shades Stamps sells on eBay with the name Kiwisteve.