I have prepared a table that I added here below, which contains the statistics of the bitcoin value growth in percentage during the last 3 years : 2015, 2016 and finally 2017. We can clearly see that the bitcoin's value has achieved an exceptional growth this year, knowing that the value is multplied in 4 in 6 months. So, in your opinion how much will be the growth in percentage during 2018 ?
A double on the price of 2017 will be fair enough for 2018's price of bitcoin. Bitcoin might end up this year at $20,000 which is 2000% from the previous year but we can't say that it will happen on the next years because of many factors. More people are now investing on it but more people will be hesitant on buying the coin at the price of $20k so most likely they will just invest on some part of it and we can't have the same increase that we experienced this year. $40,000 is a conservative estimate I believe.