How much is your car worth?

    * What you originally bought it for?
    * What you could buy that exact model year for today? From whom?
    * What you could buy a similar car for today?
    * What you could sell it for? To whom? In how much time?

And that's for something as tangible as a car, listed on the market with easily searched prices. This is a simple example, but I recall that some types of assets (land?) are valued at their original purchase price, which is far deflated from the current market value.

I think of accounting similar to benchmark tools for software -- it's all about what you want to measure, and depending on assumptions you have some wiggle room.