I remember watching some North Korea documentary where an eye surgeon was visiting to do cataract replacements. He set up in some community center and had dozen of people waiting for surgery. It can take about 10 minutes to perform the replacement and you can leave pretty quickly afterwards. It's an amazingly simple surgery that has a massive increase in quality of life for the patient. The only aftercare is an eye patch and drops to increase tear production to help heal the incision. Once a doctor has all the equipment set up, they could easily do a hundred replacements over a few days. Add to the fact that these doctors and nurses are doing work in third world countries where they may be there as volunteers and the price of the surgery is massively reduced.

>We estimate the proportion of cataract surgery patients who have bilateral blindness or severe visual impairment at 10-47% (more). We estimate success in converting blindness or severe visual impairment to moderate visual impairment of 80%-95% (more). We estimate the cost of surgery at $50-$100 (more). Hence, we estimate the cost per blindness or severe visual impairment reversed at $112-$1,250.124

Givewell agrees with the $50 figure.

You misread the report; it estimates the cost of surgery at $50 to $100, and estimates the "cost per blindness or severe visual impairment reversed" at $112 to $1,250 (with low confidence). That second number is calculated along these lines:

"[W]e suppose that a program costs $5 per person screened, that 20% of those screened receive cataract surgery at a cost of $15 for transportation and $25 for the direct cost of surgery, that 10% of those who receive surgery are blind or severely visually impaired, and that surgery is 100% effective. This program spends $650 per blindness or severe visual impairment reversed. We are highly uncertain about how close these estimated values are to the true costs and uptake of programs."

$30 dollars for an adult cataract surgery:

https://lrbt.org.pk/how-you-can-help/sponsor-a-surgery/

Most cataract surgeries in private hospitals cost around $200 in India including the lens cost. If its done in camps where multiple patients get it done the cost might primarily be lens related.