Don't get me wrong this is a great deal, but I never understand when people charge this much for shipping supposedly. Shipping a pack of seeds in a padded envelope is only about $4.50 to $5 in the US and around $9 something for a prepaid small box and both options have tracking and will be there in about 2-3 days. So why charge $15-20 if it is actually just for shipping? Unless they are paying for insurance or something then it sounds a little high.
It's totally worth it though, just sounds like they are also recouping some money for packaging or to cover the cost of making the seeds than actually just charging for shipping.