With the benefit of hindsight I do not think there were too many days during last 4 years where investing into mining hardware and power was more cost effective than simply buying BTC. Yes, at the time it often was much less risky to mine than to buy BTC. Indeed, different risk profile of buying versus mining was always obvious with GPU's/CPUs.

Note that most people who paid for ASIC's that are to be delivered soon (hopefully) paid for it when BTC was at 5$. The cost of lost opportunity for them is already nearly 300% of ROI. This means that they need to quadruple their investment just to catch up with those who decided to pass on ASIC mining and simply keep/buy some BTC instead. Good luck with this.