No no. The total amount of money is not able to buy everything in the economy. There is no such relation. It is neither equal to the available consumer goods, or any subset of what is on the market.
You're right of course that the total amount of money only buys 1/V the aggregate demand. But it does buy it, right ?
The total amount of money is equal to what value the population want to have in reserve, in money form, for short or long time, aggregated.
This is a very smart point at first sight. However:
The point is that that is the VALUE of the total amount of money times the holding time, not the amount of money itself !
Whether there is 1 kg of gold in circulation, or 1 ton, that doesn't change anything. It is not because there is 1 ton of gold in circulation, that people want to hold 1000 times more value ! Whatever is the aggregate demand of holding value, it will be "diluted" over the amount of money in existance. So any amount will do !
Of course, the aggregate demand for holding value is essentially T x M with T the harmonic average of 1/V.
In fact, you can look at the value of money in two ways: on the spending side, which is given by V x M, and related to the aggregate demand of goods and services (what I loosely called "the economy"), and on the holding side, which given by T x M.
However, you need the link with goods and services even to assign any "value" to it. After all, value is only expressed as a function of goods and services in the end. If there weren't goods and services to be bought with money, it wouldn't have any value in the end !
Bitcoins have value because:
1) you can exchange them for dollars or euros or .... with which you can buy stuff
2) you can buy stuff directly with bitcoin (as of now yet a very small fraction of the market, except the black market).
A "monetary unit" that could never be exchanged, directly or indirectly, for goods or services, would not have much value (only its intrinsic value, which is then purely collector's fun).