You can save 10x, but you need to have an x first. So if you've got formula A which costs 500 EUR, and formula B which costs 480, you're saving 20 EUR. If formula C costs 300, you could save 200, which is 10x what you would save using B. But just as people don't understand when to use 'fewer' or misuse 'literally' to mean 'figuratively' (which is rather the opposite meaning of the word they use); words don't mean anything any more, it's all about the feelings man.