I have known for a long time that the Rotring Esprit is a successor of the Rotring 400. The introduction of the Esprit must have coincided with (or have come shortly after) Rotring's decision to drop numbers in their names of pens and assign names. Another pen that was affected was the new "Newton," is a successor of the 600. One may argue that the first Newton was an improvement over the old 600 which had serious problems with the mechanism that holds the cap in place. After much use, the mechanism that makes the cap click in becomes worn, and the cap remains loose. Well, it appears that the new mechanism is not much better, as it also wears out and sometimes gets even ripped off the pen.
The 400 and the Esprit have a similar relation. It appears that Rotring tried to fix the issue with the red ring (indicating its brand) at the bottom of the barrel.
I have read post that complain that the ring came loose. It also seems that the shiny coat is very susceptible to scratches. The ends of the pen have a little spherical protrusion that does not look very good. In any case, the Esprit fixes these issues:
The red ring is now on the cap, the surfaces are matte rather than shiny (on most models, and the protrusion is gone. The Esprit truly is a "new and improved" version—something that is not necessarily true of the Newton as compared with the 600. I consider the Esprit to be one of the finest pens Rotring ever made. But, however that may be, both the 400 and the Esprit have the same nibs that they are great writers.
Why the can you buy the Esprit for roughly $30.00 on eBay, while the 400 is advertised for almost five times as much? I believe the answer is supply and demand. There are still many Esprits around, but 400s are very rare. In fact, Rotring does not seem to have produced very many of these pens. Is that irrational? Probably not. If you are a collector you may prefer something rare and imperfect, just because it is rare (like a stamp or a bill with a mistake in it). But if you are just interested in using the pen, it would be foolish to pay more for less. There is, of course, also another reason. There are sellers on eBay who believe that the name "Rotring" automatically means big profits for them. They advertise Newtons (of both generations) as 600s, and want more than $300.00 for some of them. There is even someone who tries to sell a cheap plastic pen that is available on the German eBay site for around $10.00 for eight times as much. I wonder how many of those she/he sells. Is it irrational for someone to do this? Probably not, even if greed is not a virtue. More importantly, perhaps, I do believe that it is irrational for a buyer to pay outrageous prices.
Another thing that is interesting to me is that both the 400 and the Esprit have definite similarities to the Lamy CP1. I do not know which pen was developed first, but I do see an influence or "cross-fertilization."
The Lamy CP1 is perhaps more stylish than the Esprit, but I still like to write better with the Esprit. It's not quite as thin as the Lamy and better designed for my fingers.
Should you wonder ... yes, I have an obsession with my writing instruments that is almost as intense as that of Roland Barthes, and this includes at least one piece of software.
1. I am not talking about the telescoping mini pens and pencils which were introduced later and became the "Parker Esprit." They are very different, and I don't like them. Nor am I talking about the telescoping mini pencils that have the same finish and that I like.
2. I paid a lot less for the 400 than what people want on the U.S. eBay site.