To give you an idea of just how much money is being spent on paid search, take a look at Google. Google's AdWords program is the most used pay-per-click (PPC) advertising program available today. While the tech giant owns YouTube and Android, among hundreds of other profitable brands, AdWords accounts for roughly 70% of their revenue -- which speaks wonders for its effectiveness.
Remember when you used to rely solely on search engines for traffic? Remember when you worked on SEO and lived and died by your placement in Google? Were you #1? Assured success. Well, okay, maybe not assured. Success only came if the keywords were relevant to your site users, but it was the only real roadmap to generating site traffic and revenue.