Earlier quoted context omitted.
He's Canadian I believe; so while I'm not sure how his care in NYC would be billed, I think it would be still covered by OHIP (the public health insurance in Ontario Canada) or maybe travel insurance. Certainly all the care he received in Toronto would have been covered, assuming he's Canadian.
Don't want to spark a healthcare debate, but want to mention that I bet NONE of the non-US readers on HN would have given a single thought about the costs involved if this was happening in their countries. It's wild to me that the potential financial impact of this was part of the picture for many of the US people reading it (especially the startup founders who are probably without insurance right now, and this would…
UK, and I wouldn't think about it - it's just not a consideration.
I will caveat that by saying dental care is not free[1], but the prices are reasonable - maximum charge £270 (for a single course of treatment and anything within two months of it, for treatments such as bridges, crowns, and denatures), and "If you require urgent care, you'll pay a Band 1 charge of £22.70."/ "There's no dental charge [...] if your dentist has to stop blood loss".
[1] unless you receive certain benefits