I visited on a Monday (VFS at Prestige Attrium, Bangalore). Reached by 8:30 AM(office opens at 9 AM) and there were around 10 people already waiting!!
But they have 4 counters and hence the submission completed in 15-20 minutes. They charged 2000 INR for 3 passports (primary + 2 dependents). This includes opting for SMS updates. I would suggest to not to opt for SMS updates, mainly due to two reasons. There were no SMS alerts most of the time, and whenever they came, they were all wrong or confusing SMS. So, just follow the tracking link they give after passport submission and they are reliable from my experience.
No authorization letter asked for submitting dependent passports(they did not accompany me). I did NOT opt for courier back to my address, as I have decided to collect personally.
However, while collecting the passports(allowed only between 2-4 PM, Mon-Fri), they asked for the authorization letter from dependents. Collection just took 5 minutes.