About 60k doses/lot, figure 30 endotoxin tests per lot, that's 1 test per 2k doses =~ 300k endotoxin tests to vaccinate the US.
"For now, the industry says it has plenty of horseshoe crab blood to screen coronavirus vaccines. Pharmaceutical companies test a sample from a batch of vaccines, not every dose. And that sample size, say three vials, doesn’t change whether the batch contains 100,000 doses or 1 million, says Allen Burgenson of Lonza.
In fact, Burgenson says, the industry produces enough tests in one day to screen 5 billion doses of coronavirus vaccine."
(I think this is unduly optimistic, because mfrs are likely to screen at multiple steps during production, since the latency of batches is ~100 days, and because lot sizes aren't so large yet. So divide 5 billion by a small integer).
(and then horseshoe crabs and recombinant factor C)
The FDA should figure out if fFC works and then mandate use of it if it works.