It's not just that we have $25/y now and had ~$24B/y then, to suggest it is practical. Costs are also vastly reduced over those benchmarks. Starship HLS cost the government under $3B. For that same price you could buy 30 Falcon Heavy flights at wholesale rates. New Glenn looks to launch soon and we don't know its price but it should be competitive, and it's a plenty capable ship.

Of course, depending on these as Artemis does now would only improve prices, not timelines, but it's not like commercial options are all a year old. Marginal launch has been approximately free in Artemis terms for a good while now, possibly even back in the pre-SpaceX dark ages when US launch was a monopoly flying on Russian engines with a billion dollar a year protection racket tax.

Ultimately it comes down to most of the money NASA spends on Artemis being spent on rent seeking by large old space companies that know job losses would look politically disastrous, captured in cost-plus contracts with hiring mandates, tech reuse mandates, and financial incentives not to execute. NASA is spending about as much on a mobile launch tower going overbudget on a cost plus contract as they have on Starship HLS. Guess which one had Congresspeople giving empassioned speeches about NASA's unreasonable spending habits!