On the pro side: The whole "farmed animal welfare" field in the US gets less than $100MM per year, and makes material changes to how Americans eat.
If all ~200M adult Americans gave \$1/day to animal welfare charities instead of changing their diets further, that would fund about \$7 billion of annual activism on this. That's huge. That's more than 100X what it is now. That's all US federal election expenditures during a presidential election year (but including house and senate races). That's more than twice MIT's entire budget.
In present value terms, at a 5% annual discount rate, that's equivalent to a one-time expenditure of \$140 billion. That's way more than the Manhattan Project cost, adjusted for inflation.
Seems plausible that if you could scale up current efforts to that size at current levels of cost-effectiveness, it would be equivalent in welfare impact to getting Americans off factory-farmed meat and eggs altogether. This isn't a room for more funding argument - you'd hit diminishing returns way before that point - but it does suggest that the \$1/day offset argument is not crazy on current margins, so long as you're willing to switch strategies if and when these orgs stop seeming cash-constrained (or, if you're willing to give a larger lump sum now, while such opportunities are still available.)