What exactly is the point of buying a keyword research tool when there are plenty of free tools on the market that provide a list of keywords for your industry?

There are plenty of people using these free keyword tools. You can perform basic research on any market quickly, however, at best these tools are only giving you a small subset of all relevant terms.

Chances are, the keywords provided by these free keyword tools are already used by nearly everyone in your industry. This makes it more difficult for PPC advertising. 

Although you can still profit from these industry terms, the real gold is when you can find keywords that have little competition, significant search volume, and high relevancy.