The price is purely supply and demand. Its quoted in dollars because that's the most popular unit of account.
You can also measure Bitcoin's price in ounces of gold or barrels of oil. But those measurements are also using dollars as a conversion step.
What's interesting about BTC is the supply is known. Its known exactly today and it can be predicted with great accuracy into eternity.
Most analyst price targets are based on comparisons to similar assets. If 1 BTC = $400k then Bitcoin has a market cap comparable to gold.
There are also models like Stock-to-Flow which gives a valuation based on scarcity and production rate.
Other models rely on past cycles in Bitcoin price. In the past, the peak of a cycle is 10x or more the peak of the last cycle. People extrapolate these statistics to predict the future.
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