At an organizational level, it's often not so much about money as about fairness, controls to avoid corruption, IT/supplier overhead costs, or similar sorts of reasons. I've been in C-suite, individual contributor, and everything in between. To flip things around, it's often cheaper to by a standard $3000 thing than a non-standard $1500 thing. Equipment costs are much lower than labor costs.
From my perspective, given three choices:
1. Spend $2000 of my time and $2000 of my boss' time to make an exception for a $500 monitor purchase
2. Be less productive
3. Drop $500
Often, I pick #3. I like my manager, and I don't want to complicate his life over a monitor. That lets me complicate his life over more important things, by the way.
When I was a director, I'd occasionally even spend personal dollars to buy things employees needed too. Dropping $20 is often easier than making a case to expense $20.
That being said, this is not that situation. I am a salaried employee at a small tech startup. It's always either "we have the money/don't have the money" or "I don't see the point." Luckily the latter is rare because they trust my judgment. But in the case of the former, while i get it's about resources, I'm not going to make it my problem. I am not going to fund their startup with my hardware. Which is why they are reasonable with me and just change their expectations when the resources aren't there. Of course I always try to find a solution that accomplishes the goal because I want us all to succeed, but I am not going to do it the way they want if they can't pay for it and it will only happen on my own dime.