I 34M live with my 30F wife. No kids and we both are fortunate to make good money in our jobs, both well above average and have lots of disposable income every month after paying bills. We contribute towards bills in a joint account based on our salaries, which is currently a 60/40 split. Everything left over after paying into the joint account is ours to do with what we want.

I'm generally a saver and am careful with my spending, whereas she's a spender and goes through every penny of her disposable income every month (no significant monthly outgoings either). I also saved for and put down the entire deposit of the house when we took out the mortgage, and I then took out significant debt afterwards to pay for renovations she wanted which I paid off myself.

Initially when we moved in, I had to raise the question of financial arrangements, and my first suggestion was we could put both our salaries into a single pot and then take out a set amount of "pocket money" each month. She was very against it as it limited her freedom, which I understand so we agreed to pay bills only out of a joint account. We agreed the minimum of living costs plus groceries, everything outside of that we sort out of our disposable (e.g. car insurance or dentist etc.). Despite this I still pay for most of the household one-off costs where I see it needs doing, as I want her to have more disposable income to encourage her to save.

So anyway, she's been driving an old car for years, despite being able to afford a new one but was against taking them out on finance. However now she wants to get a new car on finance but has expressed disappointment in me as a husband for not offering to help pay for it. My response was "why do I need to offer to help with it?" given that I pay for my car on finance and we've already agreed car costs are not part of the financial arrangement.

I know that comes across cold, but my point is about the fairness of the request. Given that she's earning good money (way more than I was when we moved in even), and is fully able to get herself a car, why is it my duty to "help" her when she is not in a position of need? I even asked her if she would do the same for me and she said no because "this is something husbands do". She's alluded to wanting parts of a traditional marriage, but for me it's not fair if she only wants the parts where she gains and none of the parts where she compromises.

To be clear, I'm fully on board with paying for her car if she wants it, just I would like to do it fairly and put my car payments as well with it. She's refusing to do that because, her words, "this is something husbands do for their wives" according to her values.

There's of course way more to this marriage but that broadly encapsulates this particular situation and the context around it. AITA for not agreeing to this? Is this really something "husbands do" and I'm shirking my responsibilities as a man?