A whole Ariane5 launch costs between $165M and $220M. Divide that by two satellites and it's still more expensive, per satellite, than a Falcon 9 (at $63M) -- and the satellites can't be nearly as heavy. There are instances of the lower berth being sold for as little as $60M, but that is for fairly modest satellites (relative to what an F9 can carry), and is only possible because it's being heavily subsidized by the upper berth. There's no comparison.