7500*.75 (tax) = 5,625 in net income, per month, roughly?

Most people have to pay health care, and pay into a retirement plan.

My wife makes $43,000 a year and after taxes, union dues, health care, and her 403B her take home is $1,850 a month. Or ~1/2 gross.

So OP could be closer to $3,750 take home.

If that is the case ~$450 a month + Insurance on a used car seems a bit high to me, especially since it's used and things do come up like tires, alternators, batteries, etc. You could easily add another $1,000 a year in "unexpected" non-warrantied expenses.

If insurance is $100 a month and payment is $450 + $1,000 in maintenance and unexpected expenses, we are talking about $7,500 a year cost of ownership. Or almost 20% of OP's take home income on a car.

Way to high in my opinion.

I would lease something very very cheap, like a Chevy Cruze for $170 a month, + $100 for insurance and absolutely no expenses (not even oil changes). Total cost of ownership would be $3,200 a year or just under 10%. OP could invest the other ~$4,300 a year and make money instead of putting it into an aging deprecating vehicle.

My entire goal with vehicles is the absolutely lowest cost of ownership. And I have yet to find anything cheaper than a "give me your cheapest lease" lease. Whatever they happen to be pushing the day I go in, with the most incentives. Especially when you are returning a lease and have another one in the home, add to that friends and family and good credit, it's a no-brainer. I am at ~$2,000 a year cost of ownership right now on my Chrysler 200. And that comes with the wheel and tire service, added protection insurance (up to $3,000 in extra wear and tear), free oil changes, free loaner, roadside assistance, satellite radio, 12K miles a year, and they even wash it for free if you want to wait 45 minutes ;)