Gabe here's my two cents on this matter. Anything that's collectible and a potential alternative investment is increasing in demand lately, so this crazy price escalation phenomenon is seen in many areas even though there may be alternative sources or something that will come around again and many people don't even realize that. Many people do not wait another year or two for another one to pop up. If you look at some of the insane prices on new trading cards on goldin on eBay, or the price of a limited edition sneaker or handbag for f***sake, paying $2k for anything is relatively cheap. So once the younger collectors start collecting grown up collectibles look out!
Also I've noticed that gun sellers that sell on both eBay and gunbroker (where all the Nazi stuff is sold) tend to have a lot of followers and watchers for everything and the prices are always above average and many times ridiculous. JBhenry antiques (the seller of this helmet) and especially sreisel are two of the top for this. All it takes is two stubborn inexperienced bidders to bid up an item days before the auction ends, even though eBay even states that most action happens in the last 30 mins.