That really depends which addional parts of Qt you use and what additional services you need. The core is LGPL, which is free even for commercial closed source use.
I don't know the details, but you're likely right. We certainly use more than just the core -- the core isn't where the value of Qt really is.
That said, the cost really is extreme. So much so that there is an ongoing effort to remove Qt from our products entirely. There is general agreement among the devs that the cost is not justified by the benefits, and nobody can remember why it was chosen in the first place.
All that said, I like Qt. It's quite capable and you can produce decent, portable UIs with it. But I agree it's too expensive to justify.
