$480 is pretty high for a GTX 1070 ti - quite a few of them at the $469 price point or under on Newegg most of the time (5 right now) a couple of which are at $449 (MSI blower model and Zotac mini).
$500 at current pricing is LOW for a 1080 there - exactly ONE listed at $499 (ASUS blower model) one at $509 one at $519 one at $529 and most at $539 or higher.
$20 is NOT a normal difference between comparable models of 1070 ti and 1080 cards.
Your "80% power limit" on the 1080 is for a MSI GAMING model that has a 240 "default" TDP - which is 60 watts HIGHER than almost any other 1080 ti default TDP - and the shown 180 watt draw in your picture is actually 75% TDP for THAT card, while being 100% TDP for most 1080 models.
80% TDP on most 1080 and 1070 ti cards is 144 watts NOT 180 watts.
As it turns out, in my testing on 2 1070 ti models to date (EVGA SC and Zotac Mini) vs 4 different 1080 models (Gigabyte 2-fan and 3-fan Windforce models, EVGA SC, and Zotac Mini), the most efficient point for ALL of the cards is right about 105 watts and they all hash at right about 460 sol/s at that point - for basically the SAME hashrate and efficiency on both sides of the question.
The 1080 picks up more hashrate as you bump the power draw up, but not a ton faster, so it loses less efficiency as you get closer to the rated 180 watt TDP on MOST models of both cards - but even at 180 watts it's not 10% faster than a 1070 ti while SAME MODEL versions of each card tends to be 10% or more difference in price, making the ROI longer on the 1080 vs the 1070 ti *IF YOU RUN THEM AT THE SAME POWER LEVEL OR EFFICIENCY LEVEL*.
As I already said though, if you can get a "same model" 1080 on sale for close enough to the price of the 1070 ti version, it's worthwhile - but they do NOT normally sell for a $20 difference in price for SAME MODEL cards, more commonly $50 or more price difference.
And yes, if your power cost is low enough best efficiency is NOT best profitablity - unless you're pushing the limits on available power.
4.7 is NOT average efficiency for a 1070 ti - that was a peak figure out of his video and as I recall was at the 60% TDP setting (106 watts) not 110 watts.
Average is closer to 4.4-4.5 range at the BEST efficiency point, though it's not much different at the 110 watt level (still 4.3-4.4 ballpark on average in my testing).
Trying to figure an "average" out of DSTM though is a lot tougher than EWBF, as DSTM reported hashrates bounce around a lot more from what I've seen in my testing.