Here is a pricing quote from a dealer in United States (all prices are in USD as of Oct 2011):
There are basically two different product lines, the StellaBlack product line, which is intended for commercial and permanent installation (it has heavier guage, black, UV-protected wire), and the StellaGreen product line, which uses a green wire, and uses less power because the pixels are about 10% less bright than the blacks. Before you judge that statement, understand that the blacks are REALLY bright - so bright that I never run them at 100%. Unless I run them side by side and go all solid colors you'd never notice the intensity difference.
Blacks come in 42 pixel and 85 pixel lengths, Greens come in 85 pixel lengths. Standard spacing is 100mm. Custom pixel counts and spacing are possible, in quantity, for about the same cost per pixel.
At Qty 1:
StellaGreen 85s run $129 StellaBlack 42s run $92 with screw-ups, $99 with XLRs StellaBlack 85s run $179 with screw-ups, $185 with XLRs StellaSpark strobe string - $135
There are several controller options (all come in Polycarbonite enclosures):
StellaGreen: 4 Port - $199 (External Power) 16 Port - $799 (Internal Power)
StellaBlack: 4 Port (screw-up) - $289 4 Port (XLR) - $319 16 Port (screw-up) - $1,590 16 Port (XLR) - $1,750
There are string/controller packages available as well, but there's the basic worst-case pricing scenarios. Obviously with any commercial product there's a warranty and product support, etc.