Quote from rew:
That is correct. For option trading I stick to assets that have highly liquid option chains with low bid/ask spreads. Whatever edge you might have in your trading strategy must overcome that bid/ask spread before it has a chance of doing better than break even.
Rule of thumb:
excellent spread = less than 2% of bid price, i.e. 1.00 X 1.02, 8.00 x 8.10
good spread = less than 5% of bid price, i.e. 1.00 X 1.05, 8.00 X 8.50, 21.00 X 22.00
aceptable spread = less than 10% of bid price i.e. 1.00 X 1.1, 20 X 22.
I trade all three. But if spread is more than 20% of bid, you'd better stay away.