I've got to chime in here....
To say that a seat post is just a length of tubing is a little off the mark. The seat post material we use, and any good builder should be using is a different beast. The tubing itself has to be drawn to a closer spec. than any other tube due to the fact it must fit without any issues. The 27.2 and 30.9 tubing we use is drawn to very specific tolerances for this application. This is also the reason we can't just pull a 31.6 tube off our shelf and make a seat post. Unless you are willing to buy 500 feet at a time the mill won't make a run.
Ours vs. others....
The reason our post costs what it does is due to the facts that we are using a very specific taper inside the head of the post that requires much machining of parts. We are also using 3 ti bolts and offer the ability to adjust the fore/aft and tilt independently of each other. Also, inside the Cinch post head we use 2 smooth surfaces that don't have knurling, so you won't find yourself "in-between" knurls during adjustment.
For colors, we are always noting how much or how little we are being asked to expand on what we offer…for now black, blue, red and silver/grey will be our selections….but as time goes on we’ll be testing the waters as usual.