ember - 3:03 pm on Oct 5, 2005 (gmt 0)
The only way to know is to try it. Extrapolation like that doesn't always work. Just like adding more pages and content doesn't always work because often as you add pages, your CTR decreases. A lot of this is just trial and error. You can keep upping your AdWords budget, but I'd do it slowly and keep a close eye on ROI.