This will give 1,5GHash per rig at a cost of ~4000BTC. At current difficulty it will mine 18.3 BTC per rig per day or 6679 per rig per year. This means that ROI (Return of investment) after fees will be as high as 75%/year.
Do you remember about difficulty adjustments ?
Hmm, may be I should offer such mining contracts too... :)))