I'm sure you'll get this response from a lot of thread commenter, but it depends on the the audience interests you promote to will dictate a lot of the cost.

I've never been able to get the cost of Facebook clicks down to just pennies, although I have gotten them considerably lower than what they are first estimated as on Facebook.

I've done a lot of PPC advertising in the past so I do a lot of really specific segmentation of age groups, male vs female, ad photos, ad copy, etc to get the best price I can for each click.

I think Perry Marshall is a good resource to get started with this: Facebook Advertising & Marketing Videos - some good videos here.

i read that someone get huge traffic to his site using facebook ads, he pays by vouchers,said its very cheap

How do you know for a fact that it only costs pennies? I have never been able to get it that cheap, and I do a fair bit of PPC advertising.

The average and about the lowest I can get it is at 40 cents per click.

Facebook is currently the most universal social networking Web site with more than 500 million users internationally. With an enormous base, it is logical that the conversion rate at the site could be much higher. Therefore, you could use Facebook to make cash online. The system used by Facebook advertising is both cost-per-impression or cost per click. First, choose an appropriate category for promotion. Facebook does not allow the promotion of products such as software downloads, ring tones, and cocktail. Check out the regulations of advertising to learn about the goods and services that you could publicize for the purpose of selling or causing one to want through Social Ads. The three categories most conventional are online dating sites, saving money, goods, and health or physical condition. If your goal is to use Facebook to make money, it would be better if you target your ads to serve the public who are concerned in those topics. Be strategic. To use Facebook to make hard cash through social ads, you have to study to treat it as an investment. You should spend some money for social ads. Do not worry. Video ads certainly reach the goal and probably translate into current sales, which could be the desirable way on how to make cash on Facebook.

Absolutely possible , I have send you a PM.