Ultrabooks usually have 'sufficient performance' rather than 'decent performance.
Most have ultra low power (ULV) CPUs. Like the Core i5-3317U 1.7 GHz CPU in the basic Zenbook Prime.
Which you can get for $1,130 @ Amazon - UX31A-DB51 model
Core i5-3317U 1.7 GHz CPU, 4GB RAM, 128GB SSD, 13.3" 1920x1080 LCD w/ HD 4000 Graphics.