The prices are indeed increasing every year and I expect the $20k ath to be repeated in December 2018 - January 2019.
No doubt the price of btc always rise from year to year but this year seem different because this year btc high was over $19,000 and i doubt it can be reached in this remaining quarters of the year.
N,B
This data is not correct - 17/12/2017-22 / 06/2018 Lowest price of $ 5,921 Highest price of $ 19,891 70,2%
Well, this depends on the website we're looking at. On coinmarketcap, the lowest price in this period I could find was $6225 on 22nd of June. The highest was $20001 on 17th of December. I think that this data is approximately correct and the differences might be caused by the op preferring another website (preev.com, for example, or some major exchange like binance).