Some things are obviously overstated or cited for propaganda value. For example with our ability to detect elements in parts per billion or less, it matters very much how much arsenic etc. is in them, I doubt it makes any sense to reduce those to 1 part per trillion or less.
TL:DR:
Demonstrably the existing big three, Abbott Labs and Mead Johnson produce(d) 80% of the US market share, Nestle another 18% are very weakly regulated by the FDA.
The hurdles for starting up in the US market are astronomical, and there's only one contract manufacturer Perrigo Nutritionals which not surprisingly has a large minimum order size. ByHeart became the 4th brand to have its own factory, first in 15 years.
Half of all formula is bought by the Federal WIC program, and states negotiate a monopoly with one firm.
All of the above results in prices double that in Europe, although I'd add we and the FDA are generally much more paranoid than they are, be it thalidomide long ago or COVID vaccines in the last couple of years.