And there's the even "real-er" cost of bringing in thousands of people in an ongoing pandemic (it might be hard to realize for the many Americans on this site, but many places, including Japan, are still only getting a trickle of vaccines for example).

It would be possible to just vaccinate every athlete (talking less than 10k people). It might be possible vaccinate all of the staff as well. But in a country where not even all the doctors have gotten vaccinated yet, it's not a great look, politically.

And if you choose not to do mass vaccinations, you're talking about doing a mass event with huge risks of spread at every level.