The most unethical aspect IMO isn't what they're building but the taxpayer money which those big companies are getting. These are essentially handouts.

Taxes are not paid voluntarily but coerced out of citizens under the threat of force. So when they hand out such large contracts, the government is taking from all taxpayers by force and giving it selectively to a few chosen people who happen to own shares of those companies.

Many of those shareholders aren't even US citizens!