I've some configurable products on my shop.
I've an external application that synchronize my catalog prices and quantities with a csv file.
For a configurable products that has two options for exemple, it place the difference between the two products in the super product attribute text field (fixed price).
Problem is in front-end the product price difference, and then the highest price, doesn't correspond to the one in back-end
Maybe your tax configuration is creating the issue?
Can you share the configurable price tab?
Don't know if it's relevant but I see this in Chrome Developer Tools
the correct price difference is oldPrice
Can you check if there is a Catalog Rule applied?
Yes, there are 3
First one is applied only to two categories, the product in my original post is not in one of them
Second one is applied to one category, the product in my original post is not in it
Third one is applied to one category, the product in my original post is not in it
Also if I set the rules as inactive and apply nothing changes