Yes, that would be fascinating, MadameCholet although I doubt publishers produce that kind of detailed information for reasons of embarrassment commercial confidentiality.
You can get a rough comparison from Amazon, although for digital sales only.
Bergdorf's book is currently ranked "12,184 in Kindle Store" and has 22 customer reviews, with an overall rating of 4.3 out of 5, broken down as:
5* - 63% (14 reviews) - (figures don't total to 22 due to rounding)
4* - 18% ( 4 reviews)
3* - 6% ( 1 review)
2* - 6% ( 1 review)
1* - 6% ( 1 review)
Hannah Barnes' book is ranked "3,310 in Kindle Store" and has 97 customer reviews, with an overall rating of 4.8 out of 5, broken down as:
5* - 88% (85 reviews)
4* - 7%. ( 7 reviews)
3* - 3%. ( 3 reviews)
2* - 0%. ( 0 reviews)
1* - 2%. ( 2 reviews)
(The ranking and star ratings appear below the Product Details section on each book's Amazon page for the Kindle edition. I calculated the number of reviews per star rating myself.)