http://somic.org/2010/12/14/basics-iaas-spot-pricing/

revenue_maximizing_spot_price.py

def revenue_maximizing_spot_price(n, bids):
    assert len(bids) <= n, "does not work when the number of bids exceeds n"
    revenue, spot_price = max(
        [ (sum([p for x in bids if x >= p]), p) for p in bids ])
    return spot_price, revenue

if __name__ == '__main__':
    print revenue_maximizing_spot_price(10, [ 1, 2, 5, 50 ])
    # -> (50, 50)
    print revenue_maximizing_spot_price(10, [ 1, 2, 5, 45, 50 ])
    # -> (45, 90)
    print revenue_maximizing_spot_price(10, [ 1, 2, 25, 45, 50 ])
    # -> (45, 90)