please help, adwords question

Hello everyone,
I am learning g adwords now. I have a question about the Max Bid Price.
Say i am promoting an ebook, earn per sale is $30.
Now I set up a new ad campaign, new ad group, set the ad to show only on Google Search, no search network & content network, and google ask a minimun bid price $0.1 for every keywords I bid.
My question is how much should I set the Max Bid Price when I set up a ad?

Hope I explain clearly and I'll appreciate if anyone can give me some help. Thanks.

noone can really tell you an exact ammount..
it all depends on how much you can afford.. I personally bid to whatever it takes to get the top 3 spots.

Depends on the market, but you usually want to pay a higher amount initially to develop a good quality score for your account, then lower it gradually.