What about time pressure? You'd have a hard time showing that eg MIRI would rather have a large amount of money in 70 years than a marginal 10k/year now, even discounting growth and recruitment.

You can get similar arguments for permanent poverty elimination and such; there is a certain amount of poverty that produces a certain amount of disutility every year, so money invested in permanent improvements to that now pays "interest" over time. Another way of saying this is that for permanent improvements, we are interested in the integral, not the immediate value. Delaying your donations has to take that into account.