This exactly. How sustainable are the current spends in the wake of needing ROI against these spends in the not too distant future? And who will be able to afford an upgrade cycle only 2-3 years from now given none of the capex spent will have hit positive ROI 2-3 years out.

Will everyone just accept negative ROI in the name of hype? Will scalers be able to meaningfully increase service prices without eroding customer interest?

These are all unanswered questions that a simple PE statement can't support.