I'd say you can get top-tier IEM sound quality in headphones for a mid-tier price. Just not top-tier headphone SQ for a mid-tier price. I do think mid-tier headphones usually have something to utterly dislike in their sound signature, such as overwhelming bass or sibilance. IEMs seem to have a more balanced/neutral sound for the price.
I just got the BA200 and I really like it, but I want more, now I want customs... I was looking at cosmicears, very cheap. But I might just keep the BA200s for jogging or other stuff :)
The HE-400 sounds better than any of the IEM's I had including the SM3, Heir 3.Ai and e-Q5 which are my favorite IEM's. They have all the detail with a much better dynamic sound, amazing bass thats not bloated sounding at all and the soundstage and presentation just blow IEM's away imo.
I have the HD600 out for delivery right now along with a Colorfly C3 so I'm looking forward to hearing how they all pair together.