I would say its supply/demand economics plus some whales here and there. With a 21 million supply, supply/demand will always be a problem, 7 billion people vs 21 million full bitcoins, makes sense to own at least one while you can. I prefer to buy the coins over mining even.
Not counting all the bitcoin to which the keys have been lost.
Well that's because mining has gone out of your league, gone were the days when you could mine 1000 bitcoins with a laptop and i wouldn't have bought them if i could do that now and so it s understandable where you are coming from but for me if ui had the means i will rather set up a mine and mine them rather than buy one coin for 8k$.