The best is you need to know what was the price in brand new, then the 1st year drop around 10% and then from the 2nd year around 5% for every year. This is just a general calculation. You should consider the followings:
1) car condition:
- any accident history?
- any re-paint history?
- engine condition
- gearbox condition
- brakes condition
These things are the most important things, you had better ask someone know cars go with you or take the car to your known garage to have a check before pay down payment. If seller doesn't allow you to take it to garage, then ignore him and see another one.
2) outlook:
- any colour different aroudn the car?
- car paint is too new? (looks like new)?
- too much modifications?
These will tell you what kind of persons is the previous owner, some carshop will make cars look good and sell at better price, so the 1st priority is to buy used cars from private sellers, carshop, 99% are not honest.
To judge a car is expensive or not, you should concentrate on the car condition (engine / gearbox / brakes / ac) but not only on the outlook.
Actually, if you are buying "water good", it's easy to know if the car is ok.
1) salesmen salary
2) rent for parking
3) shipping of the car from Japan
4) Profit they need to make
5) make the car outlook new (re-paint)
6) fix accident
7) environment test
8) import tax
For example a car is selling $100000, then they should make a profit around $20000, parking is say $1000/month, fix the car and re-paint ($10000), including shipping, salesmen salary. the car import price should be around $40000, so you need to think if your car can buy it in Japan for $40000, if yes, then your car should be a very good condition car, if not, then your car should be accident or flooding car.