How is "distribution cost" for artificial lighting calculated?

I've been working through "Effect of Environmental Parameters on Habitat Structural Weight and Cost" by EDWARD BOCK, FRED LAMBROU, JR. and MICAEL SIMON [1]. In particular, I'm currently interested in the discussion of lighting. But I'm unable to see where they get the "distribution cost" shown in Table 6-1 for artificial light.

The only constant mentioned for artificial lighting costs, other than the PV array, is: "The cost for light bulbs and fixtures was estimated using a specific weight of 0.03 kg/W of rated fixture output." But doing the math, starting with the 44900 kg PV array shown in the table, I get:

PVmass = 44900 kg: 44900 kg
PVpower = PVmass * 124 W/kg: 5567600 W
fixtureMass = PVpower * 0.03 kg/W: 167028 kg

The PV power calculated matches the table (0.56 kW per person in this 10,000-person scenario), but multiplying this by the specific weight of the fixtures only gives is 167028 kg -- not the 281,700 shown. Since this distribution mass (ergo cost) is the dominant factor in the cost of artificial lighting, this discrepancy is important. Can anyone see what I'm missing?

Thanks,
- Joe

[1] http://www.nas.nasa.gov/About/Education/SpaceSettlement/spaceres/II-1.html

Joe Strout -- joe@...