I marked my 15th year in the hobby this past year and my observations are:

50's GTB's - when I 1st started collecting any woodrail was $1000 or more with your sought after titles more of course. Now, these same woodrails are going for $700 and up. I sold an original unrestored working Knock Out for $4400 in 2017. Couldn't sell a nice KO project for anymore than $2000 in 2019 and it was on the market for 6 months (the guys that bought the repro playfields all finished their games and demand dropped). I was going to restore it but used the money to buy a ball bowler instead.

60's GTB's - I remember any wedgeheads with backglass animation were selling for around $1200 ea., (nice and working) Central Park, Skyline, etc.. Now, you can get them much cheaper. Titles like Kings and Queens, Buckaroo (nice and working), etc., were selling for $2200 - they're much lower now too. I think when one person (a non-hobbyist) lists a game lower than what we think it's worth , other people that sell theirs saw that lower price (on Facebook marketplace for instance) and lists theirs lower too.

70's GTB's - At the beginning it seemed as if you had the pick of the litter in small - mid sized cities as they're were not as many hobbyists back then. Lot's of good deals in the $250 - $400 range for desirable 70's games. They're harder to find in my area now as I see less of them listed but I see lots of Bally & Williams common titles just sit there and get relisted.

So, it seems as the people that played these games get older and die off, the cheaper they become - except desirable/rare titles. Some have even mentioned that in the future people might be buying them for a piece of furniture (nostalgia) and not so much to play - yikes. The same thing is happening with lower prices on slot machines, juke boxes, etc..

JMO

EM's still rule though!