This is the part even the smart people who think that they understand inflation miss.

Typical CPI vs "M2 money supply inflation" confusion. Those smart people that think they understand inflation they model it as money supply inflation, which is not the case. We have bullshit human-made consumer basket that is used to measure against known as CPI.

I remember one conversation with a really smart guy. He said something like "Once we figure out asteroid mining productivity will increase by (for discussion sake lets say) 900% and things will get cheaper.

No uh dude, if productivity increases 900%, they print 902% more money to hit the 2% inflation target measured in CPI.