I’m very lucky in that we agreed after dc2 - now 3 - id be a sahm. Dh works aboard quite a bit so it seemed sensible that I be at home and he is a high earner.
He gives me a set amount of money each month that covers my expenses - car insurance, phone bill, petrol, some of the food bill and also clothes etc for the children (we have two of them). It is just enough - just enough - to get by. After I’ve taken out the above expenses I have about £300 a month free which should be plenty but I also have the dc all the time so if I take them anywhere then it comes out of that money too. If I want anything myself - like I needed my hair cutting - I had to ask dh for the money.
Sometimes he will pay for extra things but he often says the bank is closed and he’s not spending anything else.
He has a lot lot lot more free income than me but then he’s earned it so it’s his money - I mainly struggle in the holidays when basically I’ve got £10 a day for the three of us to do anything which doesn’t go far.
My friends asked me on a spa day recently for one of their birthdays and there’s no way I could afford to go, dh goes on golf holidays / nights away for things if he wants to. But then it is his money and I have been lucky enough to stay home so I don’t know. It doesn’t always feel fair but given that I’m not adding anything I don’t know.