Potentially OP could do it. But from the wording of the comment, it sounds like OP is the main earner in the household, so if they have a spouse then the net in

Potentially OP could do it. But from the wording of the comment, it sounds like OP is the main earner in the household, so if they have a spouse then the net income opportunity cost from not working would be lower for the spouse. As to why it's cheaper, that's a calculation they have to make. If the spouse's net income (looking at marginal tax rates) is greater than 3k a month, then it's not cheaper.