All of these things are helpful in understanding an earphone, but my ultimate goal has always been to get the closest thing possible to a flat studio monitor speaker in my ear. The er4s is that conclusion. Bass is different in earphones and so far there has been no way around that. Ear acoustics change with a sealed in ear system as well. So ultimately, I want something that "sounds" the same whether these things are true or not.
With the bass issue, I find I had to simply get over that fact. Now that I am (somewhat) over it, I can enjoy something like the er4s immensely. I've listened to a large number of high-end universal iems, and in every single case where there was bass boosted or treble or any region (based on any graphs) I've found the sound to be unfaithful to a studio monitor. Because any boosted bass masks other frequencies making things sound less open and realistic. Yes, boosting the bass "might" impress some people with a more speaker like sound, but at the cost of that realistic overall sound and masking other areas.
I won't go into every single detail and area of sound, but basically you get my goal. When I listen to the er4s, I hear the open, clear, realistic, reference sound that you get with a flat studio monitor speaker. They do need a slight sub bass boost to sound "perfect", but that's pretty good compared to most. They aren't perfect, but they're the closest thing to it for my ears.
The ie800 sound pretty good, but I've heard $150 earphones I think sound better such as the pfe112. The ie800 is just missing too much in the lower treble region for me. With eq they sound great, but there's still an issue with the tips for me. The mesh screens keep them from sitting fully and comfortably in my ears without a lot of hassle. Moving them literally cuts out all sound and I have to move them again to bring it back. I'm not sure what causes this, but it only seems to be affected by the tips being "squeezed" into my ears to a certain point. This happened with all sizes. So ultimately, they just aren't for me. Horrible microphonics, tip issues and scooped out lower treble just aren't worth $1000 to me. Especially when I get what I consider to be near perfect with none of those issues for $300, or even $150 with the pfe112.
I think value is with the ears of the listener. If you love the sound of an iem, does it matter if it costs more than something else? No. Buy what you like if it's within your budget. However, I see absolutely no technical reason they should cost over three times the price of the er4s. Sennheiser is a very well known name in audio gear, and they didn't break any new ground or change nay technologies. The pfe232 sounds similar but better in my opinion, and that was $600, but could regularly be bought for $450 on some sites. Just saying, to each his own, but I would place them in more of a $200-300 bracket. Unfortunately, I don't see them going that low any time soon, if ever.