That depends on many factors. I've seen paid traffic which was targeted, but poor in terms of conversions. I've seen organic traffic from keyword without a purchase intent, which was performing really well (due to landing page quality I suppose). I also managed some FB campaigns and I received a moderate effects in terms of conversions, but with extremely low CPO due to the price, where in AdWords I'd have to pay 15$+ per click. Not mentioning that getting rankings for that keyword would take ages.