But do we know the "ideal" funding values for the pipes and museum (and if we can, then why not use that)? It's only really "unfair" if we know that the pipes "deserve" a disproportionately larger multiplier. If the pipes deserve to be funded regardless of contributions (and they probably do), then the issue is using a system that could possibly fail to provide for them in the first place.
It's not a good way to allocate funds, but I don't think it's a slam dunk to say it multiplied a larger group's money more than it did a smaller group's.