Major one, is that the Fed has basically bottomless pockets.
This is not so with any startups attempting to produce this kind of upset. The end-stage of market capitalism, is oligopoly, then monopoly. To prevent that end-game, various antitrust laws have been introduced, but all have been neutered pretty hard; In the news recently, have been many reputable stories of oligarchs conspiring to fix prices at high points, and thus to avoid any true competition of any kind.**
In order to cause the necessary competition, you need a large player to go against its own (financial) interests. This is a nonsequitor.
Now then-- Should the fed forcibly enter the market, it would be able to secure the necessary production equipment and labor, through the force of its bottomless capital. (No matter what the GOP likes to say, deficit spending of a nation that has a national bank, is by no means the same as it is for you or I.) It does not have to worry about foreclosure, or shareholders. It can simply set to work producing product.
Ideally, the prices it will set will be "Profitable." This is because forcing a pricepoint that is not profitable, would initiate a pricewar death spiral. That is not the goal here. Instead, it is to establish a viable, but "still substantially lower than conspiratorial price-fixing schemers want" price in the market. Since it is still profitable, the enterprise's returns can be diverted to the UBI. Those working the factories supplying the products, would have govt jobs, with quality healthcare and pay-- and since they would represent a large chunk of the workforce, it would force new dialog on what a "standard pay package" is. Win, Win, Win.
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In 2011, Samsung and a number of other LCD panel makers, were caught red-handed in a price fixing scheme to avoid having the prices of their displays go down.
https://www.cnet.com/news/lcd-makers-fined-388-million-for-alleged-price-fixing/More recently, Starkist tuna was caught price fixing as well.
https://www.cbsnews.com/news/starkist-price-fixing-starkist-to-pay-100m-fine-in-tuna-price-fixing-case/Last year, a rather large case was put together against many large drug makers.. For price fixing.
https://www.agg.com/news-insights/publications/recent-generics-price-fixing-filing/in 2019, there was a rash of large food companies getting caught up in price fixing.
https://www.jdsupra.com/legalnews/big-food-takes-its-turn-in-the-price-77879/Just 3 days ago, Tyson foods settled a series of cases on.. you guessed it-- Price fixing.
https://www.thepoultrysite.com/articles/weekly-poultry-digest-tyson-settles-price-fixing-casesTo combat the price fixing problem, you need a large player, that will not make such deals.