Imagine that last year my electricity cost is 2000 USD, and I mined 200 coins, I paid electricity using USD. Now I only need to sell 22 bitcoin to pay back that amount of dollar. If I paid using bitcoin as you suggested, I would have paid 100-150 bitcoins for my electricity cost
True, you can do that. But that case is the same as if you actually took your USD, and bought bitcoins at the exchange, instead of mining them. (And somebody else mined them).
I'm talking about the things that create imbalances on the exchange. In your case, the exchange did not see the increased supply of bitcoins, but the cost of mining was still there, you paid it with your USD.
If a LONG TERM projection always indicate a rise in the exchange price due to limited supply, there will be less and less people sell bitcoin to cover their energy cost, and that trend itself will lift the bitcoin price as a result, can go on for decades
Another thing, your formula is based on that most of the people could always get their hands on the latest mining technology, thus the mining competetion will always be hard. But I foresee a future that only a handful IC companies have the access to the latest engergy efficient mining technology and many normal people with ASIC miners just can not cover their electricity cost, just like what happened after 10 years of california gold rush
This also partly answered OP's question, if the mining technology becomes more and more hidden and centralized, the actual energy cost will be less and less
But that will happen under circumstances where the gain of these new technologies is diminishing.
It will not be very profitable to invest in developing 0.0003% more efficient mining hardware and any power you think you can excert from your position will be fragile at best.
In the end you will have a lot of people competing over less and less possible gain.
The risks of not getting back your investments from producing new minig hardware will increase.