The pricing for these kinds of services is really hard, because there does come a point with Internet speed where it's "good enough" and pointless to pay extra. I have a friend who's quite technical and lives in Korea, and was paying somewhere around R100 a month for 50Mbps. Even though he could get 100Mbps for R200 p/m he just can't justify (any) extra cost for the speed. With 40 Mbps VDSL you're already able to run 4+ simultaneous streams of HDX Netflix, and that is more than enough for almost any family.
Similarly to the way it was with very limited capped packages a few years ago, it was easy to think that there was never going to be a cap big enough to fully satisfy ones needs. And progressively as the caps get higher and cheaper you reach that point where you've just run out of stuff to download.
So there is real risk here especially as they struggled to persuade people to pay the R600+ 40Mbps VDSL prices before.