And maybe it was just Matt's hangover, but DHH never said "500 x $40 = $125,000." The slide actually says 400 customers @ $40/mo = $200,000/year, as you can see in the video (http://omnisio.com/startupschool08/david-heinemeier-hansson-... @ 11:50)
I also had a moment of confusion on the slide that said 400 x $40 = $200k until I realized he was talking about 12 months and rounding. I imagine something similar was happening here.
If he had said $250k I'd chalk it up to rounding for a year and accidentally saying a month.
...
Yeah, that's all I got.