Hello!
This question popped in my head as I was faking prices for my ad in the R category with old Top Gear episodes as reference.
What is the in game currency exactly?
Or rather, how to interpret it? Is it in USD? ZSD? Is it in today’s money adjusted from inflation? Or is it a completely unrelated currency?
How do I know if 5800$ in 1955 in game is any good compared to real life cars of the era?
Trying to see if the choices I make would be good enough for what I have in mind
thanks!
From what I’ve picked up from other FAQ threads, the currency that Automation uses is completely fictional. There may be a correlation between said units and other real-life ones, but as far as I know, this isn’t the case.
If you want my personal opinion, I would represent the currency as AC (or Automation Credits), but I doubt we Automationeers would blame you if you labelled the units as either AUD or NZD, and convert it from there.
Happy travels,
Antoine Renard (Krimson)
Simple answer is - you don’t 
IIRC this currency is based 2010 USD, but for forum purposes it’s referred to as modern USD, €, pounds or AM$ (Automation Dollars), each in 1:1 ratio.
How this relates to old cars - I have absolutely no idea, though when I once tried to convert a 50s car price to real money I used some dollar value calculator (to convert 2010 USD to 50s USD) and then roughly period correct dollar to złoty conversion and the price ended up more or less similar to the car I was aiming at.
For seeing how good are your choices you can use in-game demographics, though they might not be perfect if your building sth very specific.
Big-Block-chain
In each demographic, besides desireability, there is an affordability. In the kee version, that threshold was pretty static from 1946 to 2020.
Quatloos.
Automoleans 
a u t o m o l e a n s, though. :’)
Okay, so there’s no relation between in game money and IRL, the game has its own universe. Gotcha!