Thanks Carter for getting this started. I have posted a few times in various github EIP's regarding this issue and it's hard to get a straight answer that isn't somewhat dismissive.

Here is my calculated post based on my own tests and estimations. Let me know what you think. I broke it down as simplistic as possible so that anyone can extrapolate it out into the network hashrate.

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I know that you are all devs, and see this issue from one side of the spectrum, so if you don't mind, please allow me to express the flip side of this spectrum (the "bloated" miners perspective), in real dollars, so that you can take that information and see where it takes you in terms of when to expect network hashing power to drop off from the difficulty bomb.

Real world numbers as of 8/3/2017:

I'm going to use a 4 GPU rig of GTX 1060's as my example, as it hashes nicely at an even 100 mh/s. Extrapolate this out for larger operations.

Hashing: 100 mh/s
Wattage: 400w System + 50w Fan
Mid-of-the-road Electric Rate: .13 kWh
Frugal build cost: $1600

Let's assume the miner started 6/1/2017, here would be his ETH earnings (Current USD $220):

June - 2.33 ETH +512.60 -42.12 = $475.16
July - 1.35 ETH +297.00 -42.12 = $254.88
Aug - .585 ETH +128.70 -42.12 = $86.58
Sept - .285 ETH +62.70 -42.12 = $20.58
Oct - .138 ETH +30.36 -42.12 = ($11.76)
Nov - .067 ETH +14.74 -42.12 = ($27.38)
Total $798.06

So by October you'll see about 1/3 to 1/2 of hashing power drop off, because they will have no chance of recouping their ROI and will be losing money by continuing.

By November only the individuals that live near hydro or nuclear plants that get .03 kWh power will remain and Ethereum would be a stretch to still call a "decentralized network".

Keep in mind:

Miner does not hit ROI
Miner's time is valued at zero
Does not include hotter climates where A/C is required (Easily add 25-50% Cost)
With all this being stated, I hope that you can see that miners are not rolling around in piles of cash.

Please consider this calculation in your decision to reduce block rewards and continue with current difficulty increases due to the bomb.

We all want to see Ethereum succeed. If PoS was to release in full by the end of October, then perhaps the numbers work, but if the possibility of a year and a half wait time that's been thrown around is valid, then the network just simply can't sustain. Especially with a decrease in block reward.
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