Whilst you are correct in that it has a newer processor, more ram etc, but if you were to use an m8 then an m9 for the same tasks, would you notice any difference at all? I suspect not. So angry birds will probably run a few fps faster, great. The things you would actually notice like improved design or better screen are exactly the same!
If you already have an m8, you'd have to be absolutely stark raving mad to buy an m9.
To be fair...we know all that...but this is technology and as it improves the price does also. That's like saying every mobile phone which shares the same features should be priced no more than £100 as a handset of that price does effectively the same thing. (Maybe an extreme example but you get my point).
Anyone coming onto the HTC One bandwagon now won't have that consideration to make in their head though if they've come from say the M7 or another handset.
As this is technically better than the M9 despite looking eerily similar of course it is going to command the flagship price.