Looking for a gsd protection dog, what breeder and how much to pay?

I am looking for a gsd that will have the skills to deter and if necessary attack anyone invading my estate. The dog will be inside during the day and will patrol the property at night. My wife and I are planning to have children so the dog must be able to play both roles as protection dog and family dog. After researching online and calling a couple of breeding/training kennels, I find a big variance in cost, from 4,000 to 15,000. What is reasonable to pay and what breeders would you recommend? Is it risky to order from a breeder in Europe if I am in the USA? Any other tips I should know?