Some purchases are most definetely investments. A few years ago I bought a car in order to be able to commute to a well paid job. The car and fuel I've invested have repaid themselves more than ten times over (and now I don't even need to commute anymore! Hurrah! So I could even sell the car for extra profit)
I also bought myself some new interview clothes in order to get that job. I might not have got the job otherwise, as first impressions count, and my wardrobe was bare. Again, that (small, but timely) investment paid off, in cold hard cash (when combined when hard work, obviously. But hard work alone might not have done it)
Now we've got a house, we may invest in solar panels or a heat pump. Again, the idea is that they will make us a profit over the years, compared to not having them. An investment. Which would also increase the value of the house if we want to sell it.
We also invested in childcare... I kept working, built up my career... Short term hit, long term profit. Investment.
Can you invest in a baby sling or a push chair? If it creates financial opportunities that wouldn't otherwise exist, definitely! A good travel system can make the difference between being able to take baby to nursery in order to go to work, or having to stay at home and see your income crash. Investment.