Every niche is different and the only way you can know for sure is to try it on a trial basis. The vast majority of times it doesn't pay for itself as not every visitor is going to click an ad, so you might wind up paying for five clicks to generate one adsense click - which google then takes a portion of for their cut.
If your thinking like that then why not expand the idea further, your paying for traffic to get to your site that you hope to recoup by having adsense. Well adsense would just show adverts that other people are using to try and get your visitors to click on and end up buying a product/service, you coulf use adwords to advertise direct to an affiliate program like many do and make more. It's not magic power - generally is people are paying adverts that run on your sites as adsense, it is because they think they can monetise the traffic better than you are currently doing by selling them something.
yes, i myself do this... its working for me now. i have very low paying keywords, you just have to make sure your CTR is awesome. and the higher i pay in adwords, the more i make in adsense. so once i can afford to pay 1000 dollars a day with adwords i will be good.
Yeah I've heared of many people doing this. There is a rule called 'once a clicker, allways a clicker', meaning that for someone who visited your site through an advertisment is very easy to click an advertisment again. I guess it is working good, and this is my next project. Is there any tip regarding this strategy? (I am talking to those that allready do it)