I advise doing the math - the high paying niches are often very competitive. You may not get as much traffic as if you had targeted a more modest ctr niche, and therefore not as many clicks. You'll have to check whether the amount extra you're earning per click is justified given the loss in traffic.
Seriously don't pick a niche/keyword to build a site, pick everything. Why limit yourself? Build general type sites with everything under the sun, you can add content with little competition that pays ordinary and pulls a ton of traffic and supplement it with other high paying content. By building a site about Niche X, you are limiting yourself to only a small percentage of queries conducted every day then you only get a small percentage of that small percentage because you won't rank #1 for all the terms in Niche X. Also having a general content site is great for discovery and finding out what pulls traffic, and what pays well then you can skim that cream off the top and make mini sites dedicated to X and you know full well your not wasting your time on a bogus term that doesn't pay. Seriously this is good advice for people new to Adsense, i've built sites that earn in the mid-high $x,xxx per day and most of those sites were broad topics that pulled traffic for all sorts of whacky terms. Get this under your belt, use the data then delve in to profitable niche's you know are a winner before you even pay the 8 bucks for a domain.
This experiment is now 100 days old and it's time for the new site now. I would like to thank all the webmasters for the comments and feed back, for this thread. I also would like to wish you all the success in the future.