In order to fully engage with the concept, let's assume abortion is safe, affordable and accessible, and the intention of the couple not to get pregnant is mutually understood.
Then, the litmus test is simple: Is it fair for people to be forced to become parents against their wishes? If it's not fair for a woman to be forced to bear a child or have an abortion, it follows it's not fair for a man to be forced to become a parent.
Some will argue men frequently "opt out" of parenting anyway; women are then left "holding the baby" and so what difference would financial abortion make?
But if there was an opportunity for men to opt out — blame free — of fatherhood earlier, there may be fewer cases of men abandoning their children later in life. Surely it would be less traumatic and disruptive for the child if its father opts out early in a pregnancy than if he abandons it (and its mother) after it is born?
The transparency of financial abortion would also empower women, as they'd be fully aware of the responsibility they'd be taking on.
A woman who chooses to continue a pregnancy from which a man has opted out would do so under no illusions, and be answerable to no one.