is there a way to get estimated cost per word or word phrase somewhere? I'm just curios how much some words cost, I understand it may be different from reality it all depends on your quality score, but some rough number, like from - to ...
Yes adword have provided such tool - just go to Tool -> Keyword Tool -> enter keyword, choose country and press get keywords ideas button then you get search terms and monthly searches. then select Column option Estimated Avg. CPC.
Info's suggestion is the best place to start. Just remember, you will pay much more per click if you bid on keywords that aren't related to your landing page.
Use the traffic estimator https://adwords.google.com/select/TrafficEstimatorSandbox and then read the google help section to avoid questions like this https://adwords.google.com/support/?hl=en_US