Disney Auctions has a section called Purchase It Now Store (PINS) which basically sells pins at fixed prices. Some of the pins are generally available at either DLR, WDW, or the NYC 5th Avenue Store. These are available at the park price.
They also have pins that are DA only in editions of 250 ($14.00), 500 ($12.00) or 1,000 ($10.00). They also have some that are oversize or have special features and these can cost $14.00 or $18.00.
Once you commit to purchase you have ten days to send them payment; it is generally a good idea to wait until the limit as they will ship all the pins at one time; the per-item shipping cost decreases the more pins you buy at one time.
On the back of each DA Exclusive pin will be an indication of the edition size and that it is a Disney Auctions Exclusive. You will always see "Disney Auctions direct from Disney" as the seller.
Once in a while DA will put up pins with an edition size of 100 or fewer. Those will go up as Dutch Auction with generally a starting price of $18.00.
There is one last thing. They say that they don't ship to PO Boxes and their system will not accept a shipping address that indicates a PO Box address. However, they use Airborne Home for their shipping, which has a "last mile" agreement with USPS. I have found that by entering the PO Box number first (such as "123456 Box Number") instead of last there is no problem. This only works for fixed price as signature is not required.
I hope this information is sufficient and not overload.