Nice post. I think that all pinball machines will go up in value. The classics from the late 80's to late 90's from B/W will be sought after. As collectors snap these up, supply will go down. There has been a pretty steep rise of prices in the past few months. Saw a BBB listed for $40K. $40K!!! Crazy.
Tried to buy a TZ recently - you can't get into a good TZ for under $4K which is up from only 12 months ago.
My prediction: all machines increase in value, but the top 25-50 increase at a faster rate.