How to avoid unnecessary shipping fee:
multiple copies of the Basic game
When completing BackerKit survey, first click "switch your pledge level" below the green button.
Then select "$0 Reward - No reward" pledge level, and click "Switch".
If a pop-up window shows up, click "OK". This means that if some information is entered in the survey, it will be reset. Your funds pledged on Kickstarter will still count in the pledge manager, as credit.
Now click "Get Started" button and complete the pledge manager survey.
In the "ADD-ONS" section of the survey, choose any combination of add-ons. This way, if you order two copies of basic game, the shipping fee for Wave 1 will be calculated correctly.