As a business, that calculation is certainly correct. But as a charity, you have to think about what the donor would have done otherwise... maybe your $60 in marketing actually just caused the person to switch their $100 donation from some other charity to yours. Now instead of charity B getting $100, charity A only gets $40 after expenses.
Even worse, you can start an arms race. Now charity B has to spend marketing money to try to win back the donor who switched their donation to charity A, and now they spend $70 to get them to switch back (still worth it from charity B’s perspective, $30 in gain)... now we have two charities spending $130 for $100 in donations.
There is always an opportunity cost.
Is there anyone left that isn’t aware of breast cancer? What is more awareness spending getting anyone at this point (aside from non profit executives)?
It's the same for charity.
Of course all of this is the result of pragmatism and a focus on whatever it is that’s being optimized for (some aggregate impact measure which is unlikely to include employee welfare to a large extent).
But the fact of the matter is that paying salaries to people who bring in more money than they make is a good strategy for everyone, that's why non-profits do it. Even if MegaCharity A only spends 60 cents of its income on charity but MiniCharity B spends 99 cents of its income on charity, MegaCharity A is still doing better for humanity if their annual income grows every year due to the strength of their marketing. MegaCharities can raise awareness exponentially and actually change the outcomes of some of the problems in our worlds because they have the power to raise enough money in one place with one cohesive plan to actually fight these things.
I grew up next to St. Jude Children's Hospital. Everyone has heard of them. They bring in billions every year. They have an entire marketing wing and a well-compensated C-Suite (compared to other non-profits). They have way way way more impact because of all these things than most other medical charities for children. No other non-profit in the world can offer completely free medical care to children from anywhere in the world and fly their families to live near them while they're cared for without spending the kind of money they do on marketing and executives.
Non-profits need executives, and people with the credentials to be executives have to choose between non-profit jobs that pay 1/8 of what for-profit jobs do. Sure they make more than a living salary while their employees struggle to make ends meet, but that's true of every type of organization. And in the end, they won't join non-profits at all if the money they sacrifice to do so is too high.