This mother is a working mom. When she was pregnant, she continued to work (which was okay for her pregnancy -- admittedly, some moms need bed rest to have a healthy pregnancy, but each story is different). They had been trying for awhile to have a baby, so I don't know if this is how they were able to save so much, but she and her husband managed to set aside at least the equivalent of 12 weeks or so pay (her income amount) so that she could take a maternity leave without feeling stressed by the finances. This was important for them because her employer was able to give her the time off (I believe it's the law that a pregnant woman cannot lose her job over needing a maternity leave), but I don't think there was maternity pay involved in this line of work. So, as I said, she and her husband created their own cushion and "paid' themselves (by saving ahead of time).
Meanwhile, throughout her pregnancy, they replaced some of their eating out activities with spending the money on baby diapers. That may sound boring, but when new parents are looking forward to their new arrival for the first time, diaper buying together is a pretty sweet date! They are simply sharing the joy of what is coming in their lives together. Those will always be sweet memories. (If you decide to do this too, I highly recommend saving the receipts and stocking up more on size 2 and size 3 --- oftentimes babies grow out of newborn and size 1 in a hurry).
Not everyone will be able to prepare the way they did, but it's nice to know the different things people do, to help us figure out a good path of our own. I hope that this was helpful and inspiring to someone. Enjoy the preparations!