I can't tell you how many people ride the subway every day, but it's certainly less than half of the number of rides per day.
One way to explain the hospital surge in NYC is that a small percentage of people have had a highly fatal disease. Another plausible explanation is that a much larger number of people have had a less-fatal disease.
To date, we've had very poor estimates for fatality rates and prevalence. It wouldn't be shocking at all to find out that we're off by a factor of 10-, 20-, or even 50-fold.
That isn't impossible at all, given that the population of NYC is around 8.8M people. It would mean that the city is approaching herd immunity.
(I don't personally think the ratio will be as high in NYC as in LA, but that's just a hunch based on the higher testing rate.)
Basically, you're just saying that you don't want to believe what they're saying, therefore it's hard to believe. But there's nothing illogical or impossible about it in the slightest.
I am willing to bet the farm that it won't.
One factor could be the nature of transmission. Regions where transmission occurs with high viral loads entering at the point of infection (for example, hospital-acquired infections) could see more severe disease progression. You would therefore expect a high hospitalization rate relative to prevalence. It's possible in other regions, including CA, hospitalization rate as a function of prevalence is lower because acquisition is largely at lower viral loads resulting in less rapid and severe disease progression. This is, of course, a hypothesis and very likely not correct. Time will tell.
Other important factors include age distribution of infection, as well as weather conditions and prevalence of pre-existing conditions.