A little off-topic, but does amazon charge a fee for the authorization that kickstarter does before the project is successful and they charge you? In other words, do unsuccessful projects cost Kickstarter something?
If the Kickstarter project get's funded, and reach the end date, only then the pledge will be charged from your amazon account, at the ETA (if there are a lot of pledgers then it can take some time). Therefore no costs will made. So if you pledge a project who doesn't get funded, no charge will be made (;