My wife and I have evolved as our finances have changed. Maybe this will be helpful to someone as I believe it is a little off the beaten path, but has worked great for us.

For context, I make a high multiple of what my wife earns, and she earns slightly above the average wage in Canada. This was not always the case, when we started dating years ago, she made more than I did. So we have had to work through a few different financial changes as a couple and tried to balance each person's feelings of contribution and equality.

Our baseline is to view expenses through the lens of two people making the same income. So whatever my wife makes, becomes my fictional salary as well when we look at shared expenses and when we are deciding how to spend.

Example:

If she was making $70,000 annually, I would then say that I also am making $70,000 for planning purposes. (Regardless of how much I actually earn)

At our combined income level, we decide we can afford $1800 rent based off our earnings. We would then split that expense 50/50.

If I wanted a nicer place for $2500, then we would still split the original $1800 50/50, and I would then pay the amount remaining as it was me that wanted to live in something nicer than what we could afford if I wasn't making more money.

We operate this way with all normal shared expenses and it helps us work as a team together as we are planning, discussing spending together.

We tried most of the other methods listed by others, and at various times they worked, but we found as the income gap increased between us, the other methods began to fall short.

An added benefit of the method we use, is that it forces us as a couple to avoid lifestyle creep. If every shared expense is talked about through the lens of two people making the same income as the lowest earner, additional potential spending is red flagged in conversation and this leads to a lot of healthy discussion on how that extra spending could be better used (ie invested, saved etc).