Volume is a myth/scam I believe. Current unit prices with current difficulty don't make financial sense even if you get sub 5c power and 1000+ units. Even volume prices are too high to make a ROI.
Well expected ROI as if bitcoin goes to a million tomorrow the calculation changes, but you would be almost better off buying bitcoin.
So in my opinion mining is distorted by large scale scams where they calculate based on today and investors are stupid enough to believe those numbers. I think I should say in past tense were stupid enough to believe and we just see the fallout/long tail today.
It all depends individually on what goals you pursue, passive income, or earn as much money as possible?
If passive, then it is worth buying bitcoin, and in general and not only it, in order to diversify your earnings. If not passive, then it seems to me that mining the system is a good option, but $ 4000 is not enough of course, here you need to take the volume.
Yes, I think you are right for the most part, and I myself prefer to buy a coin, rather than mine it =)