Hello Krzysztof
Happy New Year.
I read your comments with great interest since I am asked occasionally to value assets or companies.
In my limited experience I have found that in the absence of a market based comparison (such as the illiquid assets that Brad refers to) DCF is the only method available.
For instance consider a solar power plant installation in a geographical area which does not have a history of solar power production (ground or roof top) at all, where DCF is the only choice.
If I understand your concerns accurately the need to document assumptions so that they can be critically evaluated applies equally to all valuation methods.
For instance, assuming you use a market based multiples approach but do not make adjustments for the reasons for the mergers or acquisitions where in some cases the value paid is mainly to take out the competition or acquire customers.
Anyway, my two cents for the cause.
Best
Savio