It's not the same price as the Adult tickets even though the booking codes are the same.

I think that "child 2-11" and "infant in seat" are basically the same fare but the person I spoke to at their call center was pretty officious on the phone, angrily asking where I'd found the fare I was referring to. (It was ITA Matrix, actually, but anyway...)

They also told me that we can't book the bulkhead if we're booking a seat for the baby as well and they claimed it was because there was someone else sitting in that row so only two seats available. But ExpertFlyer seat maps show that the rows they originally gave us (when they assumed we wanted a bassinet) in the ticket that was on hold are still empty.

I suspect they are keeping them free for people who don't pay for a seat for an infant but who want to use the bassinet -- OK, fair enough, but maybe honesty about whether the seats are actually occupied would be a better policy?