The value of bitcoin hit an all-time high of nearly $20,000 in December 2017. Less than a year later, however, its value has dropped to about $6,400, according to digital-currency website CoinDesk, whose Bitcoin Price Index tracks prices from several key exchanges.

Still, even though bitcoin is worth a lot less today than it was at its peak, if you invested $1,000 five years ago, you would have made a profit.

While the value of one bitcoin hit highs of around $1,000 and lows below $600 during December 2013, when the cryptocurrency began to go mainstream, it hovered around $1,000 early in the month. A bitcoin purchased at $1,000 would be worth about $6,400 Thursday, or over six times as much, and your total gain would be over $5,000.

This estimate does not include any additional fees or transaction costs.

If you bought bitcoin at its high near $20,000, $15,000, or even at $10,000, though, you would have lost money: around $13,600, $8,600 or $3,600, respectively.

CoinDesk: Bitcoin Price Index from Oct. 25, 2013, to Oct. 25, 2018

Volatility is pretty common for cryptocurrencies. Ethereum, once valued near $1,300, according to digital-currency tracker coinmarketcap, is now hovering around $200. Digital currencies XRP and Litecoin have seen similar declines.

That's part of the reason seasoned investors say to use caution when approaching crypto.

Billionaire entrepreneur Mark Cuban and "Oracle of Omaha" Warren Buffett, for example, have both warned that bitcoin's value is unstable. Legendary investor and Vanguard founder Jack Bogle, at a Council on Foreign Relations event, told the audience, "Avoid bitcoin like the plague."