I agree prices are way too high. Just like old bicycles, cupie dolls, etc.
The younger generations don't collect things, way out of their price range and they didn't grow up with these things around so their interest to pay or collect them is low.
There are 20/30-somethings that appreciate 1950/60's stuff, but it isn't in a collecting way, but lifestyle, going retro I believe.
Hobbies are most often carried along by people who enjoy the subject of the hobby.... kayaking, skydiving, toys, petrolina. Interests evolve and people join or leave a hobby causing costs/prices to increase or decrease. No one 20 years ago would have predicted the rise of petrolina/advertising collecting. The people who collected did so out of pure interest and shows were about that interest, not about increasing profits from sales. The hobby wasn't on a steep incline when I started selling, but around 5 years ago it became "the thing" to buy signage and such. The prices then were still reasonable and affordable. Since then the pressure has skyrocketed and prices as well.
Reproduction/fantasy signs which were mosty divided into high production Andie Rooney type or low production high quality for collectors, have become signs to deceive for profit.
At some point people will choose a new 'interest', and I think we are close to that now because the market is flooded with so many signs much discussion on Old Gas is now around whether a sign is real or fake rather than it's history.