I dont know what the purpose of your dog/ dogs is just pet companion or others. But if you stay in an apartment and plan to continue staying in one then I dont think it is advisable to get yet another big dog in the house as they require space and exercise. may be you can give them exercise 2 3 times a day etc, but still I dont think its fair on the dogs. Plus if you get an opposite sex dog, you are bound to have trouble when the lab comes in heat, specially living in an apartment, unless you plan to stray the lab or neuter the GSD. I always suggest to people to have may be just one dog but take real good care of it. Even if you think no its ok I can take care of another. This I speak with my and others I know, experience.
A GSD costing 25k to 40 odd k is generally show quality pup. The prices all depend on the pedigree and the parents. You have to decide what you are looking, as in type etc. It is always advisable to see both parents to get an idea of what the pup will turn out to be and also pick up a pup only after it is atleast 2 months +.
All the best and decide wisely.