Sci-Hub started to collect bitcoin donations early, after some of the users recommended adding a Bitcoin wallet. Bitcoin was very cheap then, and it had a reputation of an anonymous cryptocurrency that is used by hackers and shadow projects - such as Sci-Hub. In 2015 the price of Bitcoin started to grow. Sci-Hub collected some bitcoins by that time, so it was possible to buy new high-performance server. In 2017 the price of Bitcoin increased tremendously, and Sci-Hub became a very rich project. The money were enough to pay expenses for a few years.