Yes, if you look at it that way it will cost a lot of money but if you have a site with quality content and an excellent product/service that you’re selling than the targeted traffic will result in sales.
These customers you potentially have for life if you provide them with good service. Your sales should surpass the expenditure on Google Adwords and it will be a profitable venture.
Google is currently doing a beta version in the US which advertisers pay per action. Basically this means advertisers have the ability to target pages on their website, if the person browsing the site lands on this targeted page then only does the advertiser pay Google. A good example of this is if you set your ‘contact us’ page as the targeted page. A high percentage of people landing on this page will obviously give their contact details to you which could result in sales.
This idea is sure to be a success with advertisers and pay per click fraud will become non-existant.