Create new discount rule, fill fields in „Discount info“ and save.
Discount type „Assigned to manufacturers“.
In panel „Applied to manufacturers“ select manufacturer to which products discount is applied.
Add in „Requirements“ panel new „Include / exclude products by price“ requirement.
Configure requirement settings:
Action Type – „Exclude“
Price Type – „Old Price“
Comparison Type – „>=“
Price – „50“
Save requirements.
Save discount rule.