For the keyword I'm interested in, setting up an adwords ad shows that for just that one keyword in English and for all countries, I'd expect 2100 clicks per day. Setting a $1.50 maximum cpc estimates an average position of 1.5 and a cost per day of about $1200.
This seems an extraordinary amount of money. Have I got the wrong end of the stick somewhere or overestimated something?
To be consistently number one (I've never seen them anywhere other than top), do you need an average position higher than 1.5?
I've not seen an overly successful campaign that targeted one single keyword before. Your best bet is to define several phrases of 2 or more keyords that are more related to your product, and then start looking at referrer logs and begin to use negative keywords as necessary.
A highly targeted campaign can hit 20-30% CTR (blue widget in widgetland), where a general campign (blue widget) goes from 5-15%, depending on industry, ad copy, etc. It's almost impossible to say a CTR of X% is good as there are so many variables.