We were in Venice in 1999 w/Perillo Tours (which I would not recommend). We stayed in a beautiful hotel right off San Marco square -- the Luna Hotel Baglioni (owned by Summit). Since we were w/the tour, I have no idea what the per nite rate was.
Check out the "Summit Club" membership -- for $50 membership fee you get 1 free nite stay voucher + another voucher for $50 off a regular hotel stay. I have done this and have made my $50 back easily, as Summit also owns many beautiful properties throughout US and Europe.
This hotel is first class. The location can't be beat and the furnishings/baths are gorgeous (we did not have a balcony) -- good restaurant, service, etc. Good luck!
I lived in Venice for 4 1/2 months. Prior to getting our apartment, we stayed in the Hotel Atlantico. This hotel is about a two to three minute walk from San Marco Piazza and is very nice. We stayed for $100 a night. It does not compare to upper class hotels, but is very clean, quiet and enjoyable. The rooms are very ample and some have nice balcony views.
Enjoy Venice...It is the most wonderful city in the world.