Thanks jackg for your comments, but what you sommented, has nothing with Sabu protocol. The Sabu protocol doesn't care about hash-rate or "Current cost per phs" etc.
Please read the article carefully and "think out of the box". The protocol is based on UTXOs and potential valid transaction which people use them as a kind of debt-proving-document instead of sending it to Bitcoin network.
Potentially nodes would be millions or more with no limitation, since the nodes (mobile wallets) are standalone and it is not necessary everyone know everything about every transaction.