This is very simple.
The more energy is used in the creation the higher the price. It is a store of wealth because u can not cheat at the creation and know x amount of energy has been used. It will never be a currency unlike XRP's but XRP's are like sand in your hand and will never be a store of wealth, the are just handy to be used daily.
Labor theory of value?
The amount of energy used is determined by the price and block reward.
Yeah but it cant be so simple or the price would fluctuate according to this. If you look at the different epochs of mining it doesn't pan out. It could have more impact in the future. Right now it has more to do with people discovering bitcoin at a steady rate to push the price up then justify it.