At this point, might as well wait until 2021.

There is a bit of truth to this statement. There are a number of reasons why it is now very difficult to make an accurate pinball price guide:

Prices of games are rising much faster than in the past.

New games are being sold above MSRP now.

Live arcade game auctions are much rarer these days.

It doesn't seem that there aren't as many ebay auctions for pinball machines for price points (more buy it now sales it seems).

Restoration of pinball machines skews pricing compared to original games (think playfield swaps and full out restorations).

It is hard to track actual sale prices for sales that take place on cragistlist, facebook marketplace and Pinside.

Fewer people are using the Mr. Pinball daily classified ad mailing list.

Mods will significantly impact a pinball machines price. A topper can add $1k to the price.

There are a lot of various editions of games - Pro, Premium, LE. How many different WOZ editions are out there?

Remakes make pricing difficult in comparison to the original title (MM, AFM, MB, Fathom).

Information on production runs is kept secret at Stern and JJP.

Project game pricing has also increased significantly. In my early days of collecting, if a game didn't boot up, my offer price would be half of that of a working game.