In-flight WiFi and cellular were available on my last Etihad flight (Europe -> Bangkok via Abu Dhabi).
The charge was something like 25 EUR to share the 1MBit/128Kbit link with the rest of the plane.
So no wonder the uptake on this service is slow low. Business passengers will probably take it because the company pays (or it's included in the cost of their ticket) and for economy passengers it's too much to pay for a handicapped internet connection where they can't even Skype friends or browse Facebook because it's so slow.
The cell / ground based systems have a different model, and the installation costs, while high, aren't quite as high. But, the providers there, like GoGo, set the pricing, keep the branding, etc, and only share a commission back. I don't believe it's a net positive revenue for the airlines either, but I know less about that space.