I was in Ubud about 3 weeks ago and checked out Mozaic. Every guide book (and indeed the reviews listed on Mozaic's own website,
http://www.mozaic-bali.com ) show their six-course tasting menu at about US$25, but the menu I saw was more in the Rp400.000-450.000 range, which is a lot more than $25. However, by Western standards, where you can drop $30 a person for a fairly pedestrian meal, Mozaic is an incredible value and the food, atmosphere, and service are all quite impeccable. I've seen some sources proclaim it as the best restaurant in all of Indonesia, and while such praise might be a bit lofty, it's probably not a real exaggeration.
One of my favorite regular places to eat in Ubud is Kafe Batan Waru. Excellent food, nice atmosphere, and very modest prices. On Jl. Dewi Sita.