Really? Our subject never needs to do laundry? or buy clothes? or toothpaste? shampoo?
And no, 'upkeep' isn't necessary monthly. Let's look at what's necessary every so often - couple of times a year: brakes, oil changes, etc. Every couple of years or so - tires. Add those expenses up and then break them out by month.
It adds up.
Nobody buys clothes "monthly" when they live on minimum wage, and I already told you where you can get clothes in that budget. Shoot, I still stop by the Goodwill on occasion, sometimes there is some incredible finds there.
And, I forgot, the public transport in LA is better than it is in Denver by a long shot. The bus would have done fine for me. Although, as I said, I could have afforded a car. I simply chose against it to put more towards an education. Later I joined the Navy and became much less well paid, but better educated.
As for oil changes, I do those myself, as well as brakes, etc. It takes something HUGE for me to be unable to do the work myself... I've even changed out engines. I mean, the car would likely be destroyed before I couldn't fix the thing.