Hi,
While there are quite a few reputable and more or less affordable corporate localization providers, have you thought about using single freelancers instead (since you're mentioning the cost factor)?
The catch is that agencies, as a rule of thumb, will charge you twice as much as a freelancer will do to cover their project management work. Engaging a freelancer for every language will obviously involve more administrative effort, but it helps keep costs down. Plus, you'll get to know the people who actually do the loc work, which, in turn, can speed turnaround times.
As a trained and experienced translator, I could personally assist you with the German localization and might also be able to find colleagues for a few other languages. Just drop me a line if interested.
Best,
Thomas