If you don't know what you are doing with adwords you can lose money quickly.. if you are just starting out I would look into free methods until you start seeing income the you can look into paid methods..
There are four steps to get started : 1. Build a website. 2. Register for Google ads. 3. Add new content regularly. 4. Promote your website often.
You think that they charge more because people are more likely to buy from you if you are in top position. Well this isn't quite accurate, the misunderstandings hampers your ability to earn from Adword.
adwords helps in promoting your page.Once you are totally clear with adwords it will help you to earn you a lot.
You can do affiliate marketing using google adword by promoting the products from sites like clickbank, cj , jvzoo and earn lots of commission. before you do, learn from an expert. its not that easy but once you learn it, you will make more money.