Hi Kirk,
You'd need to consider the niche you're tackling - that would define competition and volume of searches for your kwds. Then I’d see if the kwds in question are some of the obvious, high-volume kwds in that niche, i.e. one or two word phrases. Then you need to decide if you want your ad to appear for these words and what are the pro's and con's of your decision...
If for example, you decide the min CPC is too high to justify in terms of ROI (which may be difficult to decide outright, since you're new to the niche) - then what will you be missing?
If I were you, I would decide how important it is for me to appear for those kwds, then see what my estimated max CPC is, and if the min CPC and my max affordable CPC are anywhere near each other, than I’d run a controlled test campaign just for those terms(keep your positions lower than the top 3). How long you run the test for will depend on many factors, but it needs to be long enough - if you know what I mean.
If you take that approach you will know what those terms can deliver - in my opinion, very often (but not always) there's a good reason for the expensive kwds to be expensive
. The competition is high on those terms because it is most likely converting - unfortunately there’s only one way to find out - spending your hard earned cash(actually you could have a very good friend in the same niche that could let you know his/her top secrets...
).
Anyway, the second option I see, is to go for more targeted cheaper kwds, and see how that goes for you - it may be very lucrative even though slower going.
It's your decision really
I can't be more specific as there are too many unknowns for me