Time to sell out??

I brought a RX470 a few months ago for AU$270.. now looking online all cards that are good for mining are sold out everywhere.  and now RX470 cards are selling for around AU$350 on ebay.  I'm trying to judge the perfect time to sell the GPU and just use that money to buy Ethereum. 

If I sell the card now I could buy 0.8 ethereum, which would otherwise take 3 months to mine and after 3 months the difficulty would be such that the card is pretty useless anyway..  check the calc here: http://www.mycryptobuddy.com/EthereumMiningCalculator


For my XFX RX470 I have set to underclock and undervolt to 0.86v which reduced the power from 80w to 65w.   Currently getting 22Mh/s

Also configured to run on task scheduler with windows startup since windows updates kept stopping my miner.  Guide here: https://www.stephenmann.net/ethereum-mining