It's easy to criticise dealers, Ebay and their prices, but in my experience spiked helmets have always been desireable, pricey items. I bought my first one in 1967 with $18 of hard earned lawn mowing ($1-$3 per lawn) money. I'd go to a couple of gun shows per year, and you might see 5 or 8 at each show, mostly Prussian M15s. There was no motherlode of them. Sometimes the dealers that issued catalogues (like Flayderman) had some, but there was nothing like the availability there is now. Cuirassier and Uhlan helmets (even m15s) were considered rare, exotic items. We live in high times for collecting. Yes, prices are high, but they always have been. The difference is, today you can surf the net and find almost any helmet you desire. I've seen more helmets on the net in 3 years than in I had in the previous 30.
It's only money.
Steve