Does Cellulaze tighten sagging skin, specifically upper thighs? Compare to Thermage & Velashape, effectiveness & price?

Yes, Cellulaze can tighten skin as part of the cellulite treatment. Thermi RF is also very good at tightening the skin on the thighs.   Results depend on the skill and experience of the doctor using the laser or radiofrequency device. The price will vary from doctor to doctor.  Experience and results are more important than price. Thermage can also achieve good results, however I personally feel Cellulaze and Thermi RF are more effective. 

Cellulaze, by virtue of having a thermal (heat) component, can tighten skin SLIGHTLY. But there is always the risk of skin injury too. There is only one truly effective and
proven lasting cellulite treatment out there, and that is CELLFINA. All of the
other lotions, potions, creams, treatments, radio frequency devices, including
Cellulaze, are at best, mediocre, and, in many cases, completely worthless.
Cellulaze is a laser-based procedure that has a much higher complication rate,
as well as a much lower patient satisfaction rate, so that answer is pretty
clear. CELLFINA is the only cellulite treatment that has a proven track record
of 96% patient satisfaction at 2 years post treatment. Nothing else is even
remotely as effective as Cellfina. I have attached a link to my website,
explaining how this remarkable system works. There are patient testimonials and
schematics reviewing the details of this remarkable breakthrough treatment.
Also, Cellfina is a single session procedure that is done under local
anesthesia with little to no pain! Thank you for your excellent question.