Another thing to keep in mind is that there is disparity even within the fiction you find in the books. There's one short story where a guy's apartment VI snaps back at his complaint of his workschedule with "Everyone works 72 hours a week," while in other books you hear mention of 50 hour work weeks being pretty regular, as well as a varying accounts of what is typical for income, relative buying power of the nuyen (you ever notice that in the fiction they almost never specify payment amounts?), and time off/vacations. Does it mean that all of these exist in different parts of the world and within different cultures? Probably. But the easiest way to put it is that it depends on the writer. I figure that if we don't have concrete, corroborative accounts of this sort of thing, it's up to the GM, and it's one of the things I both love and hate about Shadowrun. It's cliche, but I think more than in SR than with most other RPGs, it's your game, and you're going to have you're own interpretation of the world.
If it helps, for my own part, I like to imagine rough social classes and how they relate to the megas. Essentially, Shadowrun is an old school take of capitalism run rampant, and I try to keep that in mind when I present the world. The corps excercise control through their money, and when you cut through all the shell games, they get that money from the consumer. They need the little guy, and by 2080 they've largely discovered EXACTLY how far they can push people without them reaching their breaking point. By and large, they excercise soft power, and keep people content by keeping them ignorant of a better way. Bread and circuses.
So I like to think that your typical corporate wageslave is the picture of middle class. They work 10 hour shifts 6 days a week, made tolerable either by antidepressants in the water cooler or the managers simply looking the other way as long as unscheduled breaks don't get too crazy. They have great benefits, and they put up with bullshit because of the stability it comes from. The corps take a cut out of their checks for this so their actual take-home is far less than the five or six figure they make on paper, but their employers make sure to leave them with enough disosable income to go home and forget about their shitty week by shelling out for all the distractions the corp provides. They live in a modestly sized but comfortable appartment, or maybe a small townhouse, that includes a full suite of automated amenities, their typical meal consists of one portion of "real" food of some type, usually the cheap stuff, supplemented with flavored and textured nutrisoy. Might see some skilled freelancers living a similar lifestyle.
Below them I figure their are part timers and blue collar workers. A janitor, someone who works 1 hour less than overtime a week at the Stuffer Shack, or freelancers who are finding their feet or down on their luck could go here. They have more freedom from the corps but less security. They typically live paycheck-to-paycheck, and, lacking benefits, have to pay for budget insurance plans out of their own pocket for any semblance of security. They're usually stressed over the slight uncertainty of how they'll make payments next month or the pressure of debt, and, as such, find need in the escapism provided by good manufactured by the megacrops. They live in a tiny one-room apartment, kind of like what you'd expect to on the cheap in Tokyo or Hong Kong today, with a single room serving multiple purposes via appliances and furniture that folds into the wall. They mostly eat nutrisoy and similar mass-harvested foods, but can afford to splurge on some cheaper real food once or twice a week when they get really sick of their usual fair.
These two groups, I figure, comprise the "everyday" population that have SINs, and the big picture is that their lives are shitty but tolerable, and the corps keep them in check by providing whatever distractions they may need, at a cost. They may go in to debt, but the corps don't care, because in the big picture, it keeps them in legal thrall, and that's the mega's gameplan here. Do people realize it? Maybe. Some do. A lot don't. But like I said, it's tolerable for most, so those that wise up usually decide to just keep their heads down and accept the corporate comforts.