BlueBelle yes, you can buy everything it's true but not in small quantities. The box comes with ingredients weighed out so you don't end up with bits and pieces of leftover ingredients in the cupboard.
I haven't used a baking box but did enjoy experimenting with a few meal boxes when all the ingredients were included and I wasn't left with a tub of a random spice that I'd never use again.
Things you find stressful that other people don't notice.