Orbital fat removal vs. bony decompression surgery?

Is the fat removal orbital decompression surgery less expensive than bony decompression surgery? If the first one is enough for mild proptosis, what is considered mild (in terms of Hertel measuring)? (regarding thyroid eye disease - graves ophthalmopathy) Can this surgery alone make area around the eyes look better, or do a patient need blepharoplasty after orbital decompression?