I have reason to believe that you're not only wrong, but that giving up on making public transportation accessible in favor of paratransit would be a huge detriment to everyone, especially the disabled.

I live in Boston, and follow the politics and spending of the MBTA pretty closely. Their current paratransit system costs $40-$50 per trip, EACH WAY. It costs them about $100 million/year to operate (http://www.mbta.com/uploadedfiles/About_the_T/Panel/Paratran...)

It's expensive because they need large vans with wheelchair lifts, trained drivers, and service is door to door. They cover the entire service area of the regular public transport system, and coordinating rides is difficult and time-consuming. If this were replaced by a cab system, you'd have to train drivers and still get the expensive large vans. You'd need a way to guarantee service availability and reliability. That sort of thing isn't cheap.

Looking at elevators, even a very expensive 2-3 story elevator is $50k to install, and might be $10k yearly for a service contract (http://www.facilitiesnet.com/elevators/article/Economics-of-...) Certainly, the cost of elevators, escalators, and other accommodations are trivial in the MBTA budget, compared to the cost of paratransit. I've read a lot of budget documents from them, and I've never seen "elevators and escalators" as a line item. I mean, we're talking a $2 billion budget. $100 million is expensive. Even if you cut it in half somehow, it's still expensive. $1 million for elevator maintenance? Not expensive.

Because of the extreme expense of paratransit, it's difficult to sign up for the program. You can't simply arrive in Boston as a tourist in a wheelchair and expect to hop on the paratransit system. You apply, you submit records, you interview, you get issued a special account -- it's a big deal. They cover the entire service area of the existing public transport system and coordination is difficult, so you have to request a ride at least an hour before it arrives.

In addition, "the disabled" are not a group of people who just sit at home until their next doctors appointment or grocery store trip, and are happy to apply for a paratransit pickup the day before. They go out with friends, travel with friends (I've ridden the bus/subway with friends in wheelchairs several times -- it would be super awkward if they had to take a separate car), they might be running late for something, they decide they want to stop at a bar after work, or spontaneously run a few errands during a free moment. While paratransit may be very useful for some people (very sick, the elderly, patients with dementia, etc) it would be downright weird for an otherwise healthy and active person who's simply unable to use stairs.

Above and beyond that, accessibility doesn't just help the disabled. The author referenced this article: https://ssir.org/articles/entry/the_curb_cut_effect about curb cuts becoming widespread, which ended up being a tremendous help to people who were ablebodied, as well. My relatives come to visit Boston, and both my mother and grandmother have different forms of severe arthritis. For about a year after her hip surgery, my mom had to walk with a cane -- we took the elevators at every subway stop. We did the same when my grandparents were in town. I had a bad ankle sprain a few years ago and also had to use the elevators. You see a lot of people with strollers, luggage, several small children in tow during rush hour -- elevators are a huge benefit.

As a healthy, young, ablebodied person, I would never ever want the accessibility of public transport to go away in favor of "stairs for the normies" and "taxi vouchers/cash for people in wheelchairs." It's frankly a terrible plan that benefits no one.