That is a lot of money for some chicks. I am no expert, but I personally would not pay that much for a trio (but then I'm not into games either).
However, I've seen a closeup of another game bird by the same seller, and to me that seems very good in type. (from the pic in that add it's very hard to tell...) Asil being a rare bird, and quality type even rarer... I'd say if he gets that price for them, then that's what they're worth.
Same seller has a pair of (not impressive quality) buff orps for $20, so he must have his reasons for the price of the Asils - why not contact him and ask?
Now let's hear from the game fowl experts! (I really have no idea as to what the difference is between "bobby boles asils" and "simone asils"
Really though it is worth what ever anyone is willing to spend on it same with anything really.
I once bought 2 pairs of quaker parrots for $2200.00. Outrageous most will say they aren't worth more than $800. But the genetics of these two pairs gave me the following babies Green, green/blue, Blue/green, Pallid/blue, Blue/pallid & Pallid Blue. So they went from $125- $600 at the time.