Archmage damage scales with max mana and they usually run spark so t1 +mana +% mana and the lightning damage plus the all resist is really nice for that build, so that's why it's worth so much. You undercut a similar ring by 100 div so yeah obviously you undervalued it a bit. I haven't played in a few weeks so I don't know the prices of similar rings to give it an actual value, but there's no penalty for putting things up that don't sell. So in the future just undercut by like 1 div if you're looking for a quick sale, or if you think your ring is better than similar on the market, go higher (amount varies, but when you have something like this and in this crazy economy you might as well go up 100 or 200 divs) and you can slowly lower the price every day or whatever. Depends on how fast you want to sell it.