This is super misleading, from the linked website:
> Nicehash does not have enough hashing power for most larger coins, so we also calculated what percentage of the needed hashing power is available from Nicehash.
For Bitcoin, that percentage is zero which renders the dollar cost 100% meaningless.
For Ethereum, it's 7% so it's also nowhere near vulnerable from the attack vector this website is calculating a price for.
Even forgetting about that glaring issue, purchasing hashing power on NH would..drive the price of hashing power up. You would not be able to buy all the hashing power at the price that it currently trades, just like you wouldn't be able to buy all BTC or GOOG shares at the price they currently trade. This should be obvious.