I can make some back-of-the-envelope type calculations by manually watching the SERP when I type in a few words and calibrating against what I know we are spending - but are there any other ways?
This gets tedious with even a few keywords, especially when they are very competitive.
I've also found some of the competitive intelligence gathering tools to be wholly false and while I know we can't name names here, can we maybe develop some discussion around this somehow?
Honestly, it sounds as if your client is thinking of AdWords as an expense - rather than a way to reliably make more than they spend, while also sending targeted traffic to their site.
I doubt their question can be effectively answered (short of calling up the competition and asking!) and I think they are even less likely to ever be able to know how much the competition actually profits from their ads.
For these reasons, if it were me, I think I'd gently try to steer things around to the most important question, which should probably be "How much is my business making for every dollar I spend with AdWords?"
Just my opinion - and I do know it is not me that is in the hot seat on this question. ;)
AWA
I'm dealing with an Old School type client who is seeing their competition in AdWords and while I'm doing my best to sell them on the VALUE not the COST, they want to know what it might cost for them to maximize their value.
The good news is that I know a few things about AdWords, and I can see that our competitors are wasting some if not a lot of money by not knowing what I know.
Of course, I don't quite know what kind of tricks they have, but from what I can tell (and I could be surprised), they don't seem to be approaching this with much sophistication.
Short of just letting AdWords run with an unlimited budget, and / or pot-shotting at the numbers from the Keyword Tool, I was hoping there was a better way.
While not taking this as Gospel truth, it will help you develop a better sense and estimation of competitor capacity & tactics.