You might want to research that.
SPX weekly(s) at deltas around 0.15 trade in the 10s of thousands per day, with open interest heading towards 100ks. The bid-ask spread is very consistently around 40¢ for the first month (maybe 5 expiries??) -- about 1xMID for the calls, about 1.5xMID for the puts. For the third-week 'majors', the volume and open interest are about 10x the 'minor' weeklys, while the bid/ask spread is two to four times as wide.
"Well! That's unexpected!"
Yes it is.![]()
What's the option on SPX? The only option on S&P 500 is the SPY and its B/A spread is usually 0.01.

