Well, you can't be a proper father-photographer without a MF to take decent portraits of your baby. Besides, you intend to take pictures of all the family gathering, especially when you invite her relatives, whom you love so dearly. They'll be proud to have beautiful large prints hanging in their living room.

It is most common amongst photographers to buy expensive digital cameras (show her prices) when a baby is born in anticipation of the thousands pictures to be taken. It is actually your precise duty as the man of the family to take care of the documentation side of the "biologic project".

Does she really want her child to never know how beautiful she was when she was young? Time for decent portraits before it's too late.

You probably have friends of your age having babies as well. Do notice their expenditure in electronic devices.

Old mechanical cameras never really lose value. Both of you can see them as a "reserve of value". A digital camera wouldn't be the same.

If nothing else work, consider begin hiding your income from her lawyer

(in general, the advice about being a real man is very valid overall. Don't let her dictate your choices. If you feel buying the Hasselblad is right, that means it is right).