The price of bitcoin is formed exclusively by supply and demand for it. Bitcoins are not secured by any tangible assets, but the same situation is with any Fiat currencies, rubles or dollars. It is wrong to assume that bitcoin is provided with electricity spent on its mining or the cost of a bitcoin farm. The difficulty of solving the cryptographic problem during mining varies according to the network hashrate used to find the latest 2016 bitcoin blocks. If the number of miners and the electricity consumed fall several times, then the complexity of mining will simply decrease and the process will stabilize again. So the value of bitcoin and its purchasing power lies only in the public's trust in it.
Almost all top altcoins or bitcoin that has a high volume in the market are all being controlled by the whale investors, just like what is happened into XRP a couple of weeks past, same goes with Bitcoin as well. There are lot manipulators in the market, and this things can't be gone anyway. I think it is already a part of their strategy anyway.