In Ubud, I liked the Gayatri Villas. You're about 300 yards away from the Four Seasons, same beautiful view of the Ayung River Valley, fraction of the price. You can get an entire villa (ours was 3 bedrooms, 3 bath, pool, kitchen, gigantic central area, two separate buildings all to ourselves) for 275 a night depending on the season. Maybe less -- I'm not much of a haggler.

If you want to be in the middle of town, however, it might not be the right choice for you.

In Sanur, we liked the Puri Santrian:
http://www.santrian.com/puri/

IIRC, there are two hotels with that exact name, so the one I linked above is the one on the water. Nice grounds, great service, modern rooms, in the thick of Sanur. Price was pretty reasonable, too, but I can't remember the exact amount.