Actually PC sales seem to be leveling off to me. Down 11% in 2013, but only down .8% in 2014. I can also understand 2015 being slow, some (like me) are waiting for Windows 10.
Did you see what the quality the late laptops have? If I could buy (in 2010) a _decently built_ basic laptop for 400, today the only well built laptop is Macbook.
I would argue not even the macbook is well built, why in 2014 would you make a computer with 4Gb ram? But wait guys it has 4k that barley works! And the final nail in the coffin is these shitty OS releases they have been pushing out, as far as I am aware the firmware portion has been broken since Mavericks.
Well built does not mean "not underpowered". It means it will last long and has higher quality components.
What about PC parts sales?
Have they perhaps increased during the same time frame as owners swap to incrementally upgrading their machines?