A few years ago, I stayed at a delightful little place in the 7th. Hotel Muguet.
http://www.france-hotel-guide.com/h75007muguet.htm
The room was tiny, but everything was brand new, clean, and so on, with a delighful lady and her dog at the front desk. Its on a quiet little street, very close to Invalides, and a single is FF520, 2 people is up to 600, depending on the room type.