Well, that's one factor, but the other factor that I think is more important in showing that the mathematical argument put forward by the OP is nonsense is provided by serjent05:
Assuming these Billionaires do buy aggressively, then Bitcoin price maybe go way beyond the $2 million. Remember in every demand the supply react. People will tend to increase their price when they see that there is a FOMO happening in the market.
It is a clear point but people somehow missed it.
Supply and demand principle always works in short term and long term. The millionaires or billionaires can invest their money in Bitcoin market by buying bitcoins gradually or aggressively in short time but their demand will lead price up. Firstly we must think of how price reacts with massive purchases from millionaires or billionaires and we with our smaller capital can follow those whales. We fortunately can purchase bitcoins and finish our accumulation in shorter time than whales, and we can wait for chances to take profit.
OP can see this point, whales will continue their purchases as with big capital their accumulation can not be done too quickly. We can take advantage of it, and take profit when whales buy bitcoin up.