"I've been doing keyword research for years, and I can tell you that dealing with hundreds of keywords and dozens of spreadsheets is enough to make anyone lose the will to live. Keyword Researcher is great because not only does it let you easily find keywords that people are actually searching for, but it has a clean and simple interface that makes it easy to keep track of what you've found. If I'm stuck and need some new ideas, I just fire it up and usually find several things to write about in a few minutes."
This is a rather crude metric because it presumes one can monetize all the traffic they receive AND one can generate as much profit per visitor as Google does. Anyone who could do both of those would likely displace Google as the first consumer destination in their market (like how many people in the United States start ecommerce searches on Amazon.com rather than Google.com).
A service like BrightEdge comes with the biggest costs associated, but its SaaS solution for SEO covers many areas inside of a single ecosystem, including the ability to explore keyword data. This may be a benefit for agencies that wish to reduce redundancies across vendors, but eventually, it is likely that the need for a second tool will present itself as talent and effort levels increase inside of your SEO department.
If you already have a keyword list, the Free Keyword Grouper can transform your list (up to 1,000 keywords) into an organized keyword structure ready for high-performance PPC campaigns and an SEO-friendly information architecture. Just paste in your list to get back keyword groups in seconds. This keywords organizer tool will help you sort your list of keywords into structured, workable groups that can then be used for easy ad text creation. The keyword tool can also be used as an SEO keyword organizer to assist in site design.

Before you can put it to use and start making Long Tail Pro pay for itself, you first need to understand exactly what Long Tail Pro does and how it will benefit you. The number one benefit and feature of Long Tail Pro is that it helps you analyze the competition in Google much faster and more effectively than if you tried to do it only using free tools.

Given you have a good idea of where to start and are fairly confident you are speaking the same language as your client, jump start research by generating related keyphrases and long tail variants with the ever so easy to use Google Autocomplete. This tool makes predictions based on what you are typing that are a reflection of Google search activity. 

The simplest KW research tool is google. Type in your topic and scroll to the bottom to see what related results show up. Use those to either write an article or to supplement other articles with some of the keywords. Yes, they are primary phrases so you may not rank for them right away but building your site with these in it will help get rank for them eventually. Also look at what other articles that show up for the keyword use.
* Please note our tool currently assumes Google having ~ 83% of the market, with Bing + Yahoo! splitting the remaining 17% of the market. Actual market conditions may vary significantly from that due to a variety of factors including: search location, search market demographics, how much marketshare mobile search has relative to desktop in that particular vertical, etc.
Can't go wrong with the Google Keyword tool, SEMRush and Google Trends. The Keyword tool for volume estimates, SEMRush to see what keywords competitors are ranking for/targeting, and Google Trends to make sure the traffic is actually coming from countries I'm trying to target. Gives a relatively accurate picture of when to expect traffic spikes and seasonality insight.
For the first few months, there was certainly a transition period.  However, the new team was able to take over the reigns fairly quickly.  A big reason for the quick transition is because I had automated most of the business already.  So, the fact that I was stepping away didn't make a huge difference since all the sales, marketing emails, and many other details were already happening on an automated basis.