There arent really people in finance from not top 10 schools. No one from plymouth went to GS. Its not like theres really shit banks either, which don't pay well. Still clear six figures in your first year at jefferies. i'm not comparing it to averages in comp sci im comparing it to averages at google, which should be pretty high. I don't really see that as a problem with IB, if you didnt do well in school your probably pretty dumb and even if not dumb your not driven, which is what matters for IB. We're also assuming this comp sci grads go found some start up, which isn't exactly guaranteed, most probably work for firms like google, which don't pay that well. I could go fund my own HF in 5 years if im amazing and turn out to be the next stephen cohen, but thats not guaranteed.
Maybe it's different in the UK but in the US it's very difficult to get into those schools and they are graded on a curve so the percentage who don't graduate is also very high. Also keep in mind that at most major tech companies, it's standard to get stock options that match your salary, so those $300k numbers from your article are actually $600k. I'm not really trying to have a dick measuring contest between the two industries, they both pay very well, I just think tech is a safer bet right now, at least in the US.
I live alone and manage to live quite comfortably on significantly less than $100k with a savings rate of 35%. Boston is tied for highest cost of living with NYC and Honolulu.