I agree with this.
The run up in prices in the past decade reflects far more NEW cash than just the "old guard collectors" getting richer.
Like Dom said it reflects NEW demand from...
1) Young collectors who are beginning to have "Real" disposable income. If you entered the "Golden Age" niche of the hobby in 2013 or later, five figures for an entry level GA key or even a non-key issue with a coveted classic cover, seems normal.
2) International demand. The superhero movie trend of the past decade made big waves overseas too. It doesn't mean all these overseas movie-goers became comic collectors, however even one "hundred millionaire" (or billionaire) who enters the hobby may represent a large influx of cash, newly bidding on mega keys.
3) HNW to VHNW hard asset investors, who may be casual (not diehard) superhero fans, but who think nothing of dropping 500k on a Picasso drawing or vintage Ferrari. To this type of hard asset investor, 200k for a mid-grade Bats 1 probably seems cheap.
Love it or hate it, grading companies DID turn collectible comic books into "commodities" where they weren't previously. This represents a structural change in the hobby, and frankly lowers the barriers to entry for these new "investors". The advantage has shifted some, from those "old guard" collectors who have long-time "insider" knowledge and relationships, to newer "investors" who have more liquid capital.
Along with this influx of cash will come increased price appreciation (which we have seen already) -- and sharp corrections, too (maybe we will see in the coming decade?)
But a pro-longed "crash" would require a long-term decrease in demand for the asset (since the supply of GA books is fixed). From where I sit, for every "collector" who leaves the hobby, there's a new "investor" (or 2) entering it, cash in hand...