I think it's important to differentiate these situations though. A massive emergency is unexpected, and often extremely expensive. Even a responsible, financially comfortable pet owner may find themselves struggling to pay a $2,000 bill that came out of nowhere. On the other hand, spay or neuter is a routine, necessary veterinary procedure. Most pet owners know this and agree that it needs to be done. So I have absolutely no sympathy for owners who complain about not being able to afford spay/neuter surgery. You knew when you adopted that animal that it was going to need to be spayed. If you honestly can't afford the surgery, then you shouldn't have adopted that animal. Period.
I also really wish more people understood the difference in care between their regular vet and a low-cost clinic too. One of my first veterinary experiences was working for a community spay/neuter clinic. Two techs, one vet, and a clinic manager. One tech would be pre-medding, one would be prepping the animals, and meanwhile the vet was in surgery alone all day. There were two tables in the surgery suite, so as the vet finished up with one animal she would call out "Closing!" and the tech would bring in the next animal and get it set up on the second table while the vet finished up the first surgery. It was an assembly line - no anesthesia monitoring, no catheters, no fluids. Trach tubes were washed and reused hundreds of times. I was usually in charge of the "recovery beach" which was a big electric blanket on the floor. My job was to wrap animals up in towels and blankets and monitor them while they woke up, then extubate and return them to their cages. I often had as many as 15 animals lined up at one time, trying to monitor temps and breathing and blink reflexes on all of them, plus giving vaccines before they woke up. They got pain meds only if the owner was willing to pay for them, and most weren't. As soon the animal started to wake up it was returned to its cage, and that was it. No additional temp checks or monitoring of any kind, in fact most of the cages weren't even in the main area of the clinic so no one would ever know if something went wrong until it was time to go get the animal and bring it out to the owner. And the clinic manager was constantly hounding the vet and the techs to do things faster so they could crank through even more animals in a single day.
Obviously every clinic is different, but from what I've seen and heard this was a pretty decent one. The vet and techs genuinely cared about the animals and did their best for them, but since everything was designed to minimize cost and maximize efficiency, the standard of care sucked. It was one of my first real vet experiences, so at the time I saw nothing wrong with it. But looking back now, I'm shocked at how different it was from the regular vet clinics I've worked in. And most pet owners just see a lower price - they have no idea what they're compromising just to save a few bucks. Even if you tried to explain it to them, I still don't think most would understand that difference.