Bitcoin is expensive because of its popularity and high security. Nowadays, the demand of people using bitcoin is increasing, in fact bitcoin really brings many benefits in life and is a stable economic source, long-term investment, I hope the end of 2018 bitcoin will reach the value of $ 25,000.
Bitcoin has a value because of the market. It is a demand of people, therefore the limited supplies are being shared by the always-increasing demand for it. It has increased its value for the reason that back in the days when Bitcoin was still new, only few people patronized it, but when it became well-known, a lot more people have come to invest their money into it, hence increasing the value of Bitcoin.