I recently worked with a large, publicly-held company that had a six-figure quarterly budget to spend on Search Engine Marketing (SEM). A big part of the goal was to ensure we secured top billing on the very esoteric phrase that we (and our competitors!) used to define our market. I can't tell you what it was without revealing the company, but if you imagine it was something like "Enterprise Activity Management", you're close enough. The cost to secure the top slot was $14 per click!