1. No argument re LOD cables, or cables in general - but that extends well into the fullsize arena. As far as the cost of parts to make a portable amp, thats the same argument that says that Microsoft Office should cost no more than the retail price of a DVD plus P&H. Open Office (and others Open Source solutions) has been a viable free alternative for years, but we still have customers walk into our store and pay full freight for MS Office - go figure.
2. A good pair of headphones is a good pair of headphones, whether you are wearing them in a hotel room or on a bus. Its the rest of the 'portable rig' which the OP seems to question.
3. I would argue that DAPs have improved by a significant margin, but then I have never owned a *Mod anything. Those who want to persist with 10+year old Portable CDPs and tote the CDs around with them are welcome to it - IMO, that is as silly as anything else the OP is referring to in his rant.
4. End of the day, it all comes back to the Lisa III. With the (recommended) PSU and shipping, I believe thats a thousand dollar purchase (happy to hear otherwise). I would dearly love to read a comparison between the Lisa III and a fullsize equivalent, Even two years ago, I think the OP could have solved many of his issues simply by passing on his portable amp purchases in favour of a good fullsize amp - he didnt, and a lot of his post reads like regret, pure and simple.
Personally, I havent given up on the concept of a good transportable rig that I could lay out in a hotel anywhere in the world without the need for a power adapter. For those who have different priorities, its a no-brainer to spend the money on your 'home' rig or, as one HFier already pointed out, is there a law that says you cant have both ?