When was the last time you were at one? It's been a while for me, only been to the airport one in the last few years, they are quite costly and quality did deteriorate at most of them.
The one in Bayside used to always be full, even before lockdown started I hadn't seen it full in a very long while (I usually go to the Asian place next to it).
Also Spurs are quite different depending on the place, I think in Worcester was the last place I had a good cheese and bacon burger at a Spur outside of airport, but this is like 4/5 years ago, and went there as the selection late in the evening is lacking.
For spur pricing one can often go to cattle Baron or something like that and come out with a similar bill, mostly due to corkage.
You are coming from view of western Europe I am guessing, saying how South Africa is cheap to eat out in comparison or something and that food pricing and quality is fine? I highly disagree with that, sure you pay more for a steak as it's not really beef areas, and you pay more for eating out, but that's because wages are better and property prices are higher, you're still earning more generally. South Africa salary hasn't been keeping up with most restaurant price increases, that's just reflective of how the CPI is based on average and average person in South Africa is probably township and doesn't go to a restaurant at the pricing of Spur, it will rather be a township place (e.g. Langa has a really nice place if you have a friend there that's very good meat and cheap).