But we’re also taxpayers. So maybe there’s an equilibrium.

Also ideally some competition between those providers that will keep prices in line. (Spoiler: it absolutely does)

GSA also requires that the government is the lowest cost customer so nobody on earth is allowed any better deal. This also applies pressure. You have to rely on incentives in the end.

If you assume nobody has any integrity and incentives are all fake and nobody will hold to their agreements then there isn’t really a “public” good anymore anyway so what’s the point in trying to make a public cloud? It would just lead to grift at larger scale that wouldn’t even benefit our stock portfolios.