That is a bit too much money for me to risk it being fake. If I see somebody here confirm fruiting it that would give me a bit more confidence.
It looks like the fruit is as large as a chicken egg according to the pictures. That is actually a negative I think, I like the bite size kumquats where you can eat the rind & flesh at same time with no mess. The "Red Lime" kumquat hybrid is like this, it tastes okay but it is very messy to eat a whole one.