Starshield will offer secure communications to the US Space Force like SpaceX is providing via Starlink for Ukraine.

Each secure SpaceX Starshield terminal will likely charge $1000 to $5000 per month. SpaceX has proven secure communications in Ukraine that Russia could not hack. SpaceX was able to update firmware faster than Russia could hack it.

The US has the need for 100,000 to 1 million secure terminals for government, military and intelligence services. This amount could double if US allies in NATO and developed world businesses (finance, banking) decide to adopt some version of Starlink-Starshield secure communications as a standard.

1 million secure terminals at $1000/month would $12 billion per year in revenue.
3 million secure terminals at $3000/month would $72 billion per year in revenue.

Nextbigfuture has covered the technical details of SpaceX Starshield.

SpaceX is providing 20,000 secure Starlink terminals in the Ukraine. Provided in months and require constant software updates to stay ahead of Russian hacking. Proven ability to stay secure in a wartime environment against primary geopolitical adversaries. SpaceX proved to the US military and government that they can provide secure communications. If the US government adopts Starlink for secure communications in a large way like is already being provided at scale in Ukraine, then how many businesses (particularly military contractors) will adopts Starlink for secure communications?

In April, 2022, an official with the US Office of the Secretary of Defense says he was impressed with how quickly SpaceX foiled a Russian jamming attempt on Starlink dishes in Ukraine March of 2022. "In kind of the way Starlink was able to upgrade when a threat showed up, we need to be able to have that agility," Dave Tremper, director of electronic warfare at the Office of the Secretary of Defense, said during the 2022 C4ISRNET military conference.