Digging around on eBay there are several GTX 1070, GTX 1070 Ti, GTX 1080 and GTX 1080 Ti cards available. The RTX 2000 line and now the SUPER line are pushing prices for GTX 1000 cards down to more favorable levels.
An offer of $79 for a RX 570 8GB did not get a bite bit the card was not expensive new so the vendor seems to be more content to relist. RX 580 cards are also not reaching $100 which suggests price erosion is stronger.
The GTX 1070 should be around C$240-C$260 considering what it was when launched cost at $379. The GTX 1070 Ti launched at $449. The GTX 1080 launched at $499.
The EVGA GeForce GTX 1080 Ti SC2 GAMING 11GB 11G-P4-6593-KR recently sold for just under $600 Canadian.
At present many listings on eBay want close to 100% of the new cost of a card. Depreciation is not even considered. Others open at $1 and this gives a more realistic value for the video card with an unreserved auction.
The main motivation for a better video card is most driven by the LG 27UL500 which is so demanding on VRAM for gaming. Video is not a problem, gaming is the only issue.