Scary thing is, I think some of their estimates were conservative. They did not add in some things either. On the other hand, they did add in the cost of things she has owned for some time.
However, I am not really shocked by this amount given Kate's wardrobe costs have risen every year. She rarely uses separates that she can mix and match like so many of us in the business/corporate world utilize. Considering that Kate is incorporating more and more bespoke items, the cost will continue to rise.
Having said that, I do think that she often buys things very similar to items and/ or colours she already has; that is wasteful spending.
She needs a
professional stylist. One who will organize her closets and inventory her wardrobe, shoes and accessories so that she has a clear, visual catalogue of what she has (and where and when it has been worn). Until that happens, I doubt her habits will change.

Unless Charles decides to establish a spending budget.