The AP reports that Bloomberg ended the contest with 51 delegates. A quick, back-of-the-envelope calculation shows that Bloomberg spent $9,803,921.57 per delegate. The Daily Caller also found that Bloomberg had paid Democratic "superdelegates" $149,000 to give him their vote if the convention went to a second vote.
I'd say the superdelegates were a better buy in terms of influence per dollar. I'll further posit the proposition that you get more for your bribe (units of influence/dollar) with high officials than lower positioned people. The voters are at the bottom.
There may not be enough money, even in Bloomie's wallet, to buy enough of them.
“$100,000 in Facebook ads.”
Most of which were purchased AFTER the election