Economically-questionable conclusions: although individual secretive utilities might on occasion make dumb deals, they'll charge households whatever the market & regulators will allow, and then charge Amazon whatever the market & regulators allow.
And utilities would like Amazon as a customer because of the efficiencies of scale it'd provide. They'd not want Amazon at-a-loss, that then requires making other customers to pay more – and if utilities already had the market-power or case-to-regulators to charge others more, they'd already be doing it.