4 single lane roads is not the same as one road with 4 parallel lanes. Imagine you get stuck behind a truck on a single lane road doing 20 km/h. 1 km behind the truck, traffic would be at a standstill. Add in a few robots and it all translates into a nightmare.
Also, with the amount of congestion that the alternative routes are likely to take - how do you suppose that they would be able to afford constant maintenance on these roads? Maintenance translates into construction work, meaning that the single lane road is likely to be blocked for the duration of the repair, making the traffic even worse.
Waking up 30 minutes earlier to take an alternative route will therefore accomplish very little. In all likelihood, realistically you're looking at waking up 90-120 minutes earlier. So it's either wake up at 4:30am to get to work on time, or pay the exorbitant toll fees. Both options seem like very poor ones to me.
I personally think that property prices in Jhb are likely to soar as people look to start moving closer to work. If there was ever a good time to invest in property, I think it would be now.