Say I have a bitcoin that was worth $20.00 4 or 5 years ago. Say I cash it in (no idea how) and I get $20K so technically I've made a bigger than huge profit. How much of that would I have to pay in California and Federal taxes?
The difference between what you paid for it and what you sold it for (minus all fees) is capital gains.
The federal capital gains rate varies depending on your income. California has the second highest capital gains tax rate but it also varies depending on income. Cali has 10 brackets and will tax you even if your income was only $1.