It's something around 5k Euro for a new one and it's not really a car replacement. It's a fancy toy for somewhat rich people who also have a car. Cars just are not allowed to some nice places (like a dedicated cycling path on a dijk) and also are not really fun.

I have seen more cargo bikes with two or three kids in them on some kind of recreational road then I seen parked near grocery store.

For groceries, you just have bike bags. To drops kids at school or daycare, you have kid seats on a normal bicycle (one on a front and one on a back).