SamFisher/bigtexxx: Chatsworth and Van Nuys are in the San Fernando Valley, and the San Fernando Valley is part of the City of Los Angeles. It's a huge bulk of the middle-class tax base and people there occasionally threaten to secede from the city because they think the services they get are not in line with the municipal taxes they pay.
Vivid Entertainment is in LA, and shoots in LA. And lets face the truth, most p*rn is cheap off brand. Vivid DVD = $40 for like 2 hours. Cheap crappy production = $10 for 5-6 hours.
Imagine the amount of editing they'd have to do to brush out every frame at 60fps or whatever they film it at? I think you underestimate the amount of work it takes to go in and clean up frames afterwards... especially for p*rn budget.