I'm in Vancouver, WA. and my brother is in Germany. $10 is way off. $25 sounds about right.
As long as you keep it under 4 lbs., you can use first class and that's the cheapest way to go. Once you're at 4+ lbs. you need to ship via Priority mail. Unfortunately there is no surface shipping out of the US any more. Don't bother looking at UPS or Fed-Ex
Keep in mind that the shipping box and packing materials can weigh close to 1 lb for larger, heavier cardboard. You don't want to go over that 4 lb. weight limit.