It's not just state income tax making a big difference, it's also health insurance! The employee contribution towards health insurance premiums has IME ranged from $0 to $10k.
So even in the same state, two different employers paying the same gross salary could mean very different net salaries. Unfortunately, it's also a big pain in my experience to get companies to disclose this information before hiring.
Even so-called good health insurance can often have massive gaps. I'm exceptionally fortunate in that I make enough money to just pay out of pocket, if I was poor or even just working class I wouldn't be able to say drop $100 or so on an Uber ride to and out of the way doctor. I'd be skipping medicine when I can't make my co-pays, which for my extremely treatable conditions would make things much much worse.
If I had one wish it would be to decouple healthcare from employment. No one should have a nightmare scenario where they get fired on Wednesday and next week can't afford their wife's heart medicine.
So even in the same state, two different employers paying the same gross salary could mean very different net salaries. Unfortunately, it's also a big pain in my experience to get companies to disclose this information before hiring.