For one, they don't come pre-assembled. For two, if you have a problem within the year, I'd imagine Yoske would take care of that.
So, your paying a little premium for the service.
It's also important to note that Yoske doesn't like dealing with cheap bikes. Bikes being sold for $100 are typically not too well built and will have issues if you intend to keep it long-run.
You can walk into a Target and get a pre-assembled Schwinn. Or some other good brand for 200-250 or go to a second hand bike store. Got a few in Park Slope.