Can't speak for why Lou wants to do it soon, other than a chance to grift, but the earlier it's done (I think it's recommended to be done at 16 weeks? It's been a while since I dealt with this) here's a better chance that you will avoid behaviors like male cats spraying and female cats going into heat, which is better for both animal and owner, obviously. I think it also reduces some other potential health problems as well. Of course, there are going to be waitlists for the low-cost programs, which they just have to deal with if they don't want to pay a regular vet.
But at best, Lou is being too lazy to find cheap alternatives, and at worst he's just lying about the cost and being responsible to pay for it to bring in the donations. I'm predicting that this grift goes on for a few weeks, then the cat is magically fixed for cheap, and then Lou says the money he got will go towards his food and underwear money.
Edit: 30 seconds of searching found tons of places for him to look for low-income vouchers and programs to get cats spayed.
This one is in his county, around a half hour drive from him, and has the basic operation as $50, plus a bit more for tests and shots. And that was literally just the first one I saw. But his toothless mouth must be watering at that $600 estimate he will now be waving around, so that will likely be the number he sticks with.
