the cost for Voluma is very close to the "under $500" charge you quote. Perhaps if the spa is associated with a Dermatologist or Plastic Surgeon who has a large volume of Allergan products (Botox, Juvederm, Latisse, breast implants, etc.), there can be "volume" discounts or price rebates, but this charge is so very close to the cost that perhaps this is a "too good to be true" scenario.Fake products exist, as Botox has seen many imitators, so I suppose it is possible to sell bogus Voluma. You should ask to see the box as the real item has bar codes and many packaging safeties built-in. But "fakes" are still possible.If the reputation of the medspa is good, and they have been in existence for a long period of time, this should give you some comfort that you are simply getting a "good deal." But, usually, your gut telling you this might be bogus is something I would listen to. Best wishes! Dr. Tholen