Hi,
You can't use an "update the values" action for that since it will target all the prices of the products.
Instead, you want to use a "run MySQL query" action with such a query to update the price:
UPDATE #__hikashop_price as price SET price_value = 5.25 WHERE price_product_id = {product_id} AND price_value = 7;
And another action "run MySQL query" action with such a query to add a new price:
INSERT #__hikashop_price (price_product_id, price_value, price_currency_id, price_min_quantity) VALUES ({product_id}, 2.5, xxx, 75);
where xxx is the id of the currency of your prices.