Your post is actually extremely important and spells out one of the primary weaknesses of such a system. As long as the budget obtained for the vote does not have an opportunity cost with the rest of a person's wealth/budget (and I can't think of any practical way to make that happen in reality), what the voting system will in effect create is increased voting power by the wealthy, as they suffer comparatively less marginal loss from expending their entire voting budget goals towards their agenda, irrespective of their strength of belief: the downside comes from their lack of any real real-world budgetary pain.

Unless one can come up with a way to inflict the same budgetary pain on each individual for each vote-expenditure, I don't really see how you would argue for its implementation/superiority in practice (against the other forms of voting out there I mean, not necessarily contrasted just against first past the post...).

Though this all depends on what one means by "optimal voting" or "efficient", since I don't believe there can be an objective definition of such.