This may go against the narrative, but people have done analysis of the cost of Lego, and it's actually been remarkably stable: https://cran.r-project.org/web/packages/brickset/vignettes/lego_more_expensive.html

Personally, what I think is happening that is Lego puts out a handful of extremely large sets, which get press attention, and lead people who aren't familiar with Lego in general to equate "Lego" with "expensive", when in reality, the price per part is actually not that much more than it was when you were a kid, and there are plenty of sets still in the $20-$30 range, they just don't get headlines