You can use AdWords from Google, there's a tool there, which will at least allow you to see how much competition there is for a word. But you won't find the price for a single word, because that also depends on your exact content.
I guess you mean bid prices for keywords. As thhe above poster says you can check it on Adwords, but if you do not have that, you can use something like Overture. It might not be highly accurate but give a fair idea.
On adwords, would you have to enter your own bids, to see how high they go? Or is there another way to determine word costs?
checkout the link: https://adwords.google.com/select/KeywordToolExternal?defaultView=3 Enter the keywords and see the cost and popularity
By the way, do not go for the high paying keywords just because they seem tempting. You can be sure the niche will be highly competitive. Most people average below 20 cents a click here.
Thanks for the advice. Would you mind if you can give us what are the niche you think that pay high $$ per click?
I found Keyword Elite to be pretty accurate, most of the time Little pricey, but if you search around, there are 'floating' copies - but I'd recommend buying it so you can receive updates.
This is the one i use and seems acurate. And please.... don´t go to the high paying keywords if you´re new to adsense... trust me! Go first for the midle paying and work, work, work.