How do you calculate cost basis for a crypto investment?

Good day, I'm curious about calculating the cost basis for a cryptocurrency investment. Could you elaborate on the process and the factors that are considered when determining this crucial figure? Specifically, I'm interested in understanding if the calculation varies depending on the type of transaction, such as buying directly from an exchange or participating in a decentralized finance (DeFi) protocol. Additionally, I'd like to know if fees and taxes are included in the cost basis, and if there are any nuances specific to cryptocurrencies that differ from traditional asset classes.