Keyword prices have escalated on the past years as reported by Fathom Online's Gregg Stewart, senior VP-channel management and marketing. The most inherent increases came in the hospitality, retail and travel verticals.
So this may seem very obvious to you of course, yes more marketerd are using search as branding tactic so the demand is going to increase, hence so is the cost. They mention "conversion optimization" though in the article in regards to creating specific landing pages where someone clicks through and finds exactly what they are looking for...make sense? Of course it does, you don't want to search for tours to Italy and end up in Budapest do you? You definitely do not want to be searching for good restaurants to eat at in downtown San Diego and then end up at some hole in the wall, health hazard.
If you are going to dabble in the world of keyword purchasing make sure you are showing your potential customers what they want to see. Make sure you are measuring everything as well. If the demand keeps going up so will the cost and you need your budget to be flexible.