[danneu]

I recently spent just $150 in Adwords to get enough CTR data to choose from a list of product titles over a couple days. Most I've spent was $500 simply because I drilled down so deep into slight variations. The cost is really simple to figure. (How much are you bidding per keyword) X (How many clicks do you think you need for a good data set). 500 clicks at $0.30 is the $150 I spent. 500 only because I was testing between so many broad variations. You often don't need more than 100 clicks to see a clear preference trend.