But the article is missing one key ingredient – Keyword Relevancy. Deleting entirely irrelevant keywords is important, but the next step is to rate which keywords are most likely going to make money or whatever the sites goal.
Some keywords are directly on it, while others just related and only a part of the searchers will be interested in the kind of products/services your site offers.

I recommend multiplying the traffic volume by a factor (e.g. 100% for directly searching what you have to offer and 50% kind of related) to get the potential buyer volume.
This can quickly change the top targeted keywords.

PS: Don’t try to make perfect estimates. Some rough guessing will do.