There's a fairly clear misunderstanding here. I think it's absolutely true to say that money doesn't motivate people. For most people, giving them raises won't make them work harder, stay longer, be more creative, etc. - at least, not long term. And if there are problems making them unhappy, throwing money at them isn't going to help much long term either.
But if you're underpaying people or not giving raises, people quickly become unhappy and will either slack off or eventually leave - that's the 'certain point'! You absolutely need to keep giving good raises to keep good people there - but for most people it will just maintain their performance, not to motivate them to be better.