This is most odd. I've been on both sides of the fence BTW.
Have been the low earner in a relationship, my £25k vs ex-DP'S £60k and he used to take up 2/3 of the slack on things like dinner, going out and holidays. In cases where I could afford to chip in more, pay my own way, or shout dinner,bI would.
In my current four year relationship, we live together in the house I own. I'm on £46k and my DP is on £20k, when we first met in 2014, I was on £32k to his £17k, but we split stuff down the middle as we were "just dating" at the time.
Now we've lived together two years, we have both been promoted through changing jobs and yet due to our differing careers, my payrise is substantially more than his. So I knocked off £100 his household contributions to me and I've paid for our last and upcomg holidays.
We didn't really discuss it, but the way I see it is that we're a partnership, I like nice holidays and meals, so does he, but I understand that my disposal income after bills roughly equates to his take home pay and I can't expect him to try and 'keep up' with the nicer things that I / we on his salary.
When we go away, he will pay for say Airport Lounge Access, a meal or two while abroad and an excursion. Or sometimes, we go 50/50 on those things too.
We acknowledge it, for instance in January this year, I wanted to put a deposit down on a holiday, I asked where we should go, we agreed together and I paid the deposit. I said to him I can afford the installments myself and can he pick up the tab to and from the airport and of course cover his own spends. He agreed.
For me, it's not how much you take home as such, but how much you've got left over after the bills. Why wouldn't I want to share what I have with my DP, with no hesitation?
Good luck sorting it. :)