Sustainable Organic traffic takes time to build and it also builds authority and credibility. It is like Free lunch, which is liked by everyone and it has its benefits which can be reaped for a long time after the hard work is done on the foundation whereas paid traffic can get you instant traffic and conversions and you have to spend instantly for it. Paid traffic also requires a lot of testing on ad units and finding a gem which gives you high number of conversions than other ad units to get the maximum out of the ad campaign.