The total # of competing pages is not the best way to evaluate KW volume, as those are pages that just happen to mention the KW anywhere on the page and may not be pages that are actually very hard to compete with. It also may include lots of pages that arent even about your niche directly.
So once you think you have a good key phrase search for Key phrase
Then check for "Key phrase" in quotes which will only show pages with that specific phrase
then check
allintitle: "key phrase" which only shows pages that have the keywords in the title of the page which gives you a better idea of actual competition.
Now you can look at the top listings in the allintitle search to see what they are doing to get up high and see if it would be hard to beat them. Check to see if the top listing are dominated by big authority sites or smart small marketers and affiliates that have lots of links or what. Sometimes you can find a niche that appears to have some competition but once you drill down and look you can see that there really isn't very stiff competition.
HERE'S a great example of a key phrase someone used as an example in a marketing video I watched for some product they were trying to sell.
canon G7 camera (broad match) 1.4 million competing pages (looks too competitive at 1st glance.)
canon G7 camera - Google Search
He drilled down with his KW tool to find "canon G7 price" (in quotes) only 145 competing pages.
HE WAS ABLE TO GET IN THE #2 SPOT with a little SQUIDOO PAGE!
Here's the search page:
"canon G7 price" - Google Search
Here's his little Squidoo page which comes up #2 for me.
Canon G7 Price on Squidoo