I can see how it all adds up, too.
It's all very alien to me, because I work in welfare rights and am used to doing financial capability work with people on very low incomes. But looking at those kind of numbers, I can see that there's not a huge amount spare, especially if there's a car on PCP or a loan and if the home is a flat with service and maintenance charges.
I also realise that in a highly paid job, there's often an expectation that employees look immaculate, so costs for hair, clothes, dry cleaning etc, and that the work can also come with an expectation that you join in expensive work social events for networking purposes.
This is the most expensive time though, OP, when there's no help with childcare costs and everyday expenses are increasing. It will get better, there are some great suggestions upthread, especially around salary sacrifice for childcare, and some of the childcare costs will be covered by "free" hours come September. And you're probably "time poor", so that the last thing you feel like doing after a day's work, commuting and dashing to nursery is to roast a chicken to feed you both for a few days or make a nourishing soup from scratch.
It does, and will, get better.