Hi,
Your filter is on a brand but your screenshot is of a variants listing. Variants don't have a brand linked to them.
So you can't do it like that.
You could use the product_parent_id to target all the variants of a product, but you would have to do it one product at a time.
So it might not be suitable.
In your case, I'm afraid the best is to directly run a MySQL query in your PHPMyAdmin like that:
UPDATE #__hikashop_price AS price SET price.price_value = price.price_value*1.1 WHERE price.price_product_id IN (SELECT product_id FROM #__hikashop_product WHERE product_manufacturer_id = 75);
where #__ is replaced by the table prefix of your Joomla configuration to match with the tables in the database.