Promote a RX 470 with "custom mining bios" with adjusted memory straps on Craigslist and I bet newbie miners bite.
What you are doing is plain fraud. Never cheat a newbie into believing something that is not,everyone starts from zero and never be an ass to take advantage of people who does not know anything.@ OP mining difficulty will keep on increasing and there is nothing you can do about that,make the most when you can and get out when you think that profit is not that good.
I intended that more as a joke, actually.
Actually I have seen cards on Ebay that are pre-modded for Ethash.
I would not call it fraud either , they would be getting exactly what they paid for and won't have to tinker with the bios or anything.
If they fail to understand difficulty, then that's their problem.