i think you can buy an equivalent prefab home these days for about $125k. A bit of inflation over $84k, but not approachable. But the appreciation formula for such types of houses hasn't changed - still lower than traditional stick or stone.
But hey, rebate!
Ah, yes, the popular urban myth that houses in cities are made of gold and platinum (or similarly expensive materials) while the houses built on the periphery are doomed by planned obsolescence. Thank you for telling us that isn't the case.
You've got the permits, the foundation, driveway, utilities, and the whole issue of paying someone to put the parts together, to name a few.
But not in San Francisco.