i stayed for 2 weeks in an excelent Hotel called Shinagawa Prince Hotel.
I payed 600€ for the plane (Frankfrut GER- Narita JP).
Hotel price was 500€ for 14days (cheeper is possible, i payed extra for the excelent view+smoking room)
I also bought a JR Rail Pass for 2 weeks for Narita and Tokyo (costs 3000Yen ~30€) which allowed me to
use the train for 2 weeks in tokyo which is totaly necessary because you need trains every day in tokyo.