I have a Polaroid SX-70 camerea in excellent condition: only the most
minor wear on it.  But in searching through pages of SX-70 web sites,
and many Ebay auctions, I can only find one other camera that looks
anything like this one, and it was simply listed as "rare."

The camera is a Polaroid SX-70 Land Camera (with no modifier: not an
alpha, a Model 2; just an SX-70); it is black with chrome trim around
the viewfinder and the lens (most SX-70s have tan trim and chrome
bodies).  The shutter button is red.  Serial Number is: 2C621459055. 
What is the value (or range of values) for this camera?

"Current prices are 10-90 $"

http://www.chemie.unibas.ch/~holder/SX70.html

About halfway down the page, the site owner states the price and also
that it is "it is neither expensive nor rare"

However, if there's a lack of them on ebay and other websites, you
could charge pretty much whatever you wanted, within reason of course.

(save your $15)

According to the Hove International price guide for collectable cameras 

 Polaroid SX-70   $80-$150  (as of 2005)