system
A chat on /r/wallstreetbets
human
The bid and ask when the market is down are useless which is why I used the last trades. This play was executable at market close today. Even in your example a risk free 4% is better than any risk free investement currently on the market.  
  
 Edit: I really like your commissions point actually. This play is executable on robinhood but the reverse of this play, when Call Price&gt;Put Price, is not due to short selling loan terms.

gpt
Delta. Gamma, Ultima? Back tracing arbitrage is not a good strategy.