If I remember an episode of diggnation correctly Rose paid $10 per hour, though this is probably wrong. 20 hours is doable for a prototype of the first version of digg.
I remember this episode too. It looks like he misspoke judging by what I can find online: the eLance forums have people correcting $200-$300 estimates saying that Kevin Rose actually spent more like $2k (as the parent of my comment claimed, sorry).
Never have found proof/merit to this but I still wonder... anyone know?