It's also automated driverless trains, something that probably be raised when comparing costs.
MUNI handles 157,000 daily riders. The TEL line is expected to hit 500,00 in some years, maxing out at 1M in the distant future.
It's not that big of a difference.
This is one line in a subway network of many, handling 3x more people than the entire MUNI network from opening day (of the full line). The Singapore MRT as a whole already has a daily ridership of 3,400,000.
Sure capacity is higher but the comparison is like 2-3x not an order of magnitude.
Pre-COVID projection for SF Central Subway is 43,700 daily trips by 2030, and maxing out at 65,000. So yes, order of magnitude difference in capacity.