Much of this is steeped in buyer psychology. The best marketers in the world know that there is a psychological process that must occur for prospects to whip out those credit cards and turn into buyers or even hyper-active buyers. One such person whose perfected this process is Russell Brunson, an "underground entrepreneur" who founded a company called ClickFunnels, a sales funnel SaaS business that empowers marketers from around the world to build marketing automation without all the hassle.
If you're wondering what a sales funnel is, simply imagine a real-world funnel. At the top of that funnel, some substance is poured in, which filters down towards one finite destination. In sales, something similar occurs. At the top, lots of visitors arrive who may enter your funnel. However, unlike the real-world funnel, not all who enter the sales funnel will reemerge out from the other end.