If it actually costed $20 everyone would be playing Taleb on much of their portfolios :). It is not cheap, and also not so easy to size everything properly. Hedging is not user friendly at all.

Robert Shiller often complains about the lack of general public awareness when it comes to hedging. Rationally, if you work in an oil company you should be short oil, but the opposite is much more common to be found in the real world. Similarly with real estate - if you have a big mortgage maybe you should somehow be short on the real estate market elsewhere, just in case your city becomes the next Detroit.

For those unfamiliar with it: options are usually quoted per-share (even though almost all of them are sold in contracts of 100 shares), because it makes calculating the break even price a lot easier. For a put costing $20 on a $165 strike, the break even at expiration is $145.

Also, you never buy long dated puts ATM in bull markets with the intention of hedging. It's usually much further OTM, since it becomes a lot cheaper. Right now all options are very expensive due to high implied volatility.

You are correct, my math was way off. Buying ITM options is definitely not the best way to protect capital.