The difference between persuasion and manipulation

I’ve often heard people (well marketers) say that the difference between persuasion and manipulation is if the end result is good. Sometimes it’s a variant of this and might focus on the motivation rather than the end result but I really question these statements.

After all, I might believe that this product/service/course will help someone but what if they spend money which they shouldn’t on it? Does that mean they were manipulated or does it mean they are bad financial planners?

Most dictionaries seem to focus on who benefits from the change. Do I, the one talking/writing, benefit? Then it’s manipulation. Do they, the one listening, benefit? It’s persuasion.

That makes sense but is tricky in marketing.

In marketing, the one talking always benefits and they may even convince themselves the customer or client is benefiting (when they aren’t).

I still don’t think I have a clear answer, or one that I’m completely happy with, but I’m happy to continue wrestling with these questions and raise a questioning eyebrow whenever a marketer dismisses claims of manipulation.