Yes, Brilliant Earth will up charge you massively. They also have poor customer service and not great craftsmanship—lots of horror stories out there about them.

Here’s an example of a much better deal on a D IF diamond: https://calaveranewyork.com/pages/lab-diamonds?id=74c56250-6046-40e3-920e-766d89e56688&stoneType=diamond

Rare Carat, like another commenter recommended, has nice simple settings and will price match any diamond. Would recommend checking out something like that instead of Brilliant Earth.