So this guy is not doing his calculations at today's Zcash price of ~$175, but instead of a (hopeful) future price of $245 to make his calculations. So "if" Zcash goes up another $70 he will be making $5/day with a $660 investment in GPUs (not including the system).
So we have two scenarios, one invest $660 in GPUs today to earn $5/day (again if the price goes back to $245) and two just take that $660 and buy 3.77 Zcash coins. (I am leaving system costs out as to make the example easier.)
So let's look at the mining route. The 3 1060's are making closer to $3.60/day right now as Zcash is actually trading at $175 and not $245. So $660/$3.60 is 183 days to ROI. If the price does go back to $245 we are looking at only a 132 day ROI, which is quite good actually.
If we instead invest in Zcash we have 3.77 coins in our wallet for the same $660 investment. Those coins are worth $660 today, so in effect you already ROI on them. If the Zcash price "pops" back up to $245 as per the posters argument, your Zcash would then be worth $923.65. This represents a $263.65 profit.
If you are mining instead and the price pops up to $245, you still need to mine for those 132 days to just pay off the GPUs, much less make the extra $263. To earn the full $923.65 you would need to mine for 184 days even using the $5/day profit target.
I think most miners also calculate the resale value of their GPUs as a hedge which your calculations don't account for above. Granted this summer has been an anomaly when it comes to GPU resale pricing, but even getting 50% of the original value of your GPU a year after purchase is probably do-able.
So... add an extra $1000 from that initial $2000 GPU purchase investment.
The problem with the hedge argument is if the mining profitability were to go poof I do not think you would get 50% for you cards. One factor is most retail prices are actually 150% of MSRP. So a card that normally would sell for $200 such as a RX580 8 GB is going for $300+. So if the market collapses you will not be selling a "normally" $200 card for $150 (which 50% of the overpriced $300 you paid) but probably closer to $75 which is a little more than a 50% drop from the MSRP. And even this may be too generous as there is a lot more GPUs out there now than back when scrypt mining went away.
Also the hedge as you put it is still offset by the pure profit buying coins would give you. So instead of hoping for ROI in 6+ months and then hedging by selling your GPU, you could come out just as much or more by buying the coins directly. Also in the event of a sudden and violent market downturn, it is much easier to get in and out of coin potions that it is a mining setup.
I disagree, but we can agree to disagree.
There are still plenty of miners who will snatch up your GPUs at a reduced cost because they have cheap power or are willing to stick it out. And the gaming market is much larger than the mining market, and gamers are always on the lookout for a bargain GPU.