Costco (COST, news, chart, volatility) short-term puts are seeing action after an investor bought 10,000 November 50s and sold 10,000 November 47.5s for $1.15. This is possibly an opening spread as volume exceeds existing open interest. If so, it is a bearish short-term bet against the retailer, as it comes one week before the November options come off the board. The breakeven on this spread is $48.85 with a possible payoff of $1.35 if COST falls to $47.5 or less. The debit is at risk if shares settle at $50 or more. No news on COST today. Shares hit a low of $48.21, but have since bounced back and are trading up 20 cents to $50.17.