Due to all the bullish enthusiasm around Bitcoin (BTC -0.88%) and the new spot Bitcoin ETFs, it's unsurprising that we're starting to see some very aggressive price estimates for Bitcoin. The one that is getting all the attention, of course, is the new $1.5 million forecast from Cathie Wood and Ark Invest.

While $1.5 million might sound like an impossibly high pie-in-the-sky number for a single cryptocurrency token, you'd be surprised at how easy it is to find million-dollar price estimates for Bitcoin. In fact, you can find $10 million, $100 million, and even $1 billion forecasts for Bitcoin. So, just how realistic are any of these price estimates?

Past results are no guarantee of future performance

The most common approach for coming up with a $1 million price target, quite simply, is to look at how Bitcoin has behaved in the past and then extrapolate how it might behave in the future. Once you examine the price history of Bitcoin, you'll quickly see how easy this is. For example, it took Bitcoin approximately six months to 10x in value from $1 to $10, another six months to 10x from $10 to $100, and another six months to 10x from $100 to $1,000.

Older investor with hand on chin, thinking.

Image source: Getty Images.

So, you can see where I'm going with this. If you rely entirely on past performance, you could fall into the trap of assuming Bitcoin can routinely increase in price by 10x every six months or so. At a current price of $50,000, that gets you to a price of $500,000 by mid-2024. If you assume Bitcoin can double in price over the following six months, then voilà! You've arrived at $1 million in Bitcoin by the end of the year. Congratulations!

There are different variants of this approach, of course. One of them involves considering the halving, a blockchain-specific event that occurs only once every four years. As a result of this halving, Bitcoin tends to skyrocket in value. If you examine the history of three previous halving events and assume Bitcoin will perform similarly after the next halving event (scheduled for April), you can come up with some dizzying price assumptions for Bitcoin.

Market sizing comparisons

Another approach to creating a $1 million price for Bitcoin involves market sizing comparisons. By comparing the value of Bitcoin to the value of another well-known financial asset, you can come up with some pretty impressive numbers.

For example, since Bitcoin is often referred to as "digital gold," it could make sense to compare the market value of Bitcoin (currently around $1 trillion) to the value of all the physical gold in the world (which is about $13.7 trillion). If you buy into the argument that "digital gold" will eventually crowd out "physical gold" as a store of value, then you've found a very clever way to show that the value of Bitcoin could increase by a factor of anywhere from 10x to 15x. That gets you to a $500,000 price for Bitcoin pretty quickly.

But do the numbers make sense?

My concern is that, at some point, the numbers stop making sense. For example, given the current circulating coin supply of 20 million for Bitcoin, a target price of $1 million assumes a market valuation of $20 trillion for Bitcoin.

But think about that number for a second. That $20 trillion is nearly 7x the market cap of the world's most valuable publicly traded company (Microsoft or Apple, take your pick). It's approximately equal to the annual gross domestic product (GDP) of the United States. And it's roughly half the combined value of the S&P 500, now estimated at $40 trillion.

In short, a $20 trillion valuation for Bitcoin is possible only if there is a huge shock of some kind to the entire U.S. economy. Unfortunately, that probably means a market crash of some kind. In such a scenario, money would presumably flow out of dollar-denominated financial assets and into Bitcoin very rapidly.

Cathie Wood's $1.5 million price forecast

With all credit to Cathie Wood, I think she has the best $1 million valuation model for Bitcoin. It's based on looking at Bitcoin's use cases, extrapolating future growth prospects, and then aggregating the values of these different use cases. And the math behind the model is completely transparent and publicly available, so you can check the numbers yourself.

That said, I have a hard time seeing Bitcoin hitting $1 million anytime soon. Sure, Bitcoin might be trading around $1 million sometime within the next decade. But just be careful about listening to anyone who tells you that the price of Bitcoin is skyrocketing to $1 million in 2024 simply because Wall Street now has Bitcoin ETFs to sell you.