I think you hit the nail on the head - an assurance vs. not.
So how important is the $75K?
One thing I didn’t like that you said was “my parents really want me to go the CS/DS pathway”.
It’s not their life - it’s yours - and at 17, you don’t know what you want as you said - and that’s a good thing. It gives you a chance to explore.
In the end, it’s easier to start in the harder to get major and if you decide to pivot, and say, for example, go to math - then you can.
But not so easy as you note to go the other way.
UIUC is far and not the easiest to get to - although you can fly there. The weather will be different and the campus will be different - have you visited?
It’s really a tradeoff - savings and convenience - but a very real possibility that you can’t study exactly what you want - although you can certainly find something quant and STEM heavy at UCB.
In the end, I hope you study what you decide you want to study and not what others want.
As for what you should do - only you can decide. I’d go UIUC - but that’s because i’m risk averse and to me, attending a school without the assurance of studying what you want is a wasted opportunity. But I’m not you.
Best of luck.