My impression was not based on price as I don't own any of them. I happen to find all of them at the meet to compare on the Reference monitor. I was lucky enough to run into UE there to demo the monitors and try to compare them, and to me, without any consideration of price, the AK trumps all the Fiio players.
Reason why this was surprising was the I had on the back of my mind as AK being overprice and of course Fiio being more reasonably priced, but I've never been a fan of Fiio DACs or Amps, but X5 sounded ok, and AK series much better.
Would I purchase the AK? No, I would not pay that much, but I thought it was interesting to find out which ones were the top with a very transparent IEM. Do I think AK is worth the price tag, I don't, but what I came to realize is that it's fantastic sounding DAP/Sources for those they is willing to take the plunge.
I suggest all to test out them all with a top iem that is very revealing.