The value of an investment can be determined several different ways:
In some markets, one method is more appropriate than another. For example, in real estate, method #1 above is most popular. The downside, of course, is that comparable investments must be easily identified and they must have changed hands recently. Otherwise, there's no way to identify the proper appraisal value. In other markets, building the asset from the ground up is the only way to identify its value.
The video below discusses the market for some valuable works of art.