I am new to sapphires and I am looking into untreated sapphires with royal blue color to add them to my jewelry collection. However, the price offers by some sellers for untreated blue sapphire is ridiculously low.

For example, in Thai and Vietnamese gems market, an 10*8mm oval sapphire with blue color in this video was claim to be untreated and only costs about $500, which I think is unbelievably low. I don’t want to risk buying beryllium treated sapphire so I would love to hear opinions about whether gemologists fail to detect beryllium treated sapphire. If that is the case, I would rather pay 10x-20x that price but for a real untreated stone with GIA report here in the US.