How much were the 1070's 6 months ago?
Most were around $410 give or take $30, with the "water cooled" cards closer to $500.
That's NewEgg pricing, BTW - I gave up on eBay a long time ago when they started pushing Paypal as their primary payment method.
410 is very high for a 1070
I bought a g1 gigabyte 1080 for 450 3 months ago
Not on NewEgg you didn't, unless it was a refurb on sale.
Let's stick to apples and apples comparisons here.
Also, if you're going with the "lowest" figure, a lot of 1070 cards were on sale at various times on NewEgg at $379 (thus the "give or take $30" part of my comment) - though WHICH ones in any given week varied.
The cards actually at $410 or so would have been mid-range to higher-end cards, like the EVGA FTW models or the Gigabyte Gaming models, as opposed to the lower-end stuff like the EVGA "SC" and Gigabyte "G1" and "ITX" models.