For those saying "that's what TI is for" or "why would they fly if sick?", I don't know of any TI policies that cover you if you choose not to fly because you are sick and don't want to infect others. They only cover you if you are assessed as being medically unfit to fly, which is not the same thing.
TL;DR; you fly when you're sick because TI says you won't get covered if you're not hospitalised, and your flight is non-refundable.
I probably could have (if push came to shove) found accommodation in Reykjavik for 5 or 10 days - but I was still testing positive 10 days later.
I could have afforded to pay for new business class airfares at peak season from Reykjavik to Melbourne, if I'd had to.
But TI would not have helped.
More to the point, they'll do very little for you when you are very sick in terms of offering on the ground assistance. My father - 88 years old and with pre-existing morbidities caught covid in 2022. TI covered COVID and his pre-existing conditions (and would want to - cost him $4500+).
Travel insurance basically said "sure, if he's hospitalised, we'll help, but until then, good luck".
Local health (Iceland) were great, we were in a remote area, arranged a phone consult for us, told us how to arrange emergency medical care if we needed it, where to turn up if we felt we could drive there, or to call an ambulance if we felt we couldn't, but basically said "sorry, we don't have antivirals in Iceland, so there's not much more we can do other than offer advice on symptomatic treatment". The doctor did provide a phone script for some drugs that would be OTC in Aus but were script in Iceland for us to pick up in the nearest town (150km away).
Unsurprisingly, 3 out of the four of us caught it. I got it worst as (at the time we left) I wasn't eligible for a booster, and so I hadn't had a recent vaccination, and got quite unwell.
Guess what; my travel insurance said the same thing: we'll cover you if you're hospitalised, otherwise, good luck.
So, I jumped on that plane, P95 masked up for other passengers' and flight crews' benefit, and flew to New York via Vienna, coughing all the way, with fever and rigours. And spent five days in New York in bed.
It's not that I didn't know, or didn't care, but that I didn't have a spare $15,000 for accommodation and new flights to do the right thing, having been told that TI wasn't going to help until I was hospitalised.