Bitcoin is open, borderless, decentralized, neutral, and free to participate. The network works no matter the price. With adoption lagging the capability of the network, many new startups will pay you to try their service. This is a common growth strategy to attract new users on a cost-per-customer acquisition strategy. So not only is the network of money free to join, you might get free money out of it in the form of signup or referall bonuses, subsidized by venture capital.