Much like how gold and other things got expensive, it is how much people are willing to pay for it. You have to remember thst crypto currency is based on supply and demand (like any other commodity) and price would move depending on how much people are willing to pay for it. I just don't know the technical side of it.
Usually the thing with something that has value. Sure, a lot of people may be seeing it more as a speculative asset right now, but that does not change the fact that bitcoin has a lot to offer to so many of us in the long run considering how we will surely get to be able to have freedom from banks and all the governmental policies that has been screwing up a lot of things over the years.
It is just very simple, over time as demand keeps increasing, and there is limited supply as we all know, which is what makes bitcoin deflationary; it is the need for it that will keep driving the value up.