As a side note, I remember both WWI and WWII helmets were everywhere. It seemed that they were at every garage sale, and at every estate auction.
I was just a kid then, but all the adults I ever talked to said "Those helmets will never be worth anything. They made millions of them. If you are going to collect, get the German stuff, but wait until the price comes down. It is way too high right now."
At that time, US helmets from WWI were selling for $5 to $10, and WWII were $5 on the high side.
The coolest German helmet I've ever seen in person was a real Afrika Korps helmet with full liner and decal that a US soldier had mailed home, with the address written on the outside crown of the helmet, and it sold for a whopping $45, which was considered an outrageous price at that time. I literally begged my mom to let me buy that helmet...she thought I was a monster from Mars for even wanting it. That must have been about 1980 or so.
If I could go back in time...