> someone who bake cakes for a living who said they used boxed mixture for most of their baking.

Would love to see such a video. I could imagine using certain box mixes for certain specific purposes, but for most of their baking? I cannot imagine this being claimed by even a casual cook/baker.

> some of the ingredients involved are not easily available/cost-efficient for the home baker

Sure, but some of these are also only necessary because the box has to have a very long shelf life. If you buy your staple ingredients every month or two, you don't need stabilizers and such.