How to determine the cost of a startup?

We all heard about sales and purchases of various startups. When it comes to the stock exchange, IPO, the situation is more or less clear - the value of shares is determined by the market. But still it is necessary to reach the exchange.

Here we are talking about how the cost of startups is determined when they are bought by investors or business angels. For example, Yandex bought Loginza for $ 300,000. Why for 300, but not for 150 or 500? Where did this amount come from? Is there any method of determining the cost of a startup?

On Habré wrote about it a few years ago.
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For example, the estimated annual income of the project when it reached the estimated level. For example, it is expected that the project will bring in $ 300,000 a year. So, you can buy it for $ 300,000 and expect that the investment will pay off within a year.

At the same time, it is often difficult to estimate the expected income from a new project (by statrapp I understand a project that has no direct analogues), since there are no examples of the development of such projects, and it is not known whether it will go or not, and if it does, then and what will turn into.

What do you think?