  We present a strategy-proof public goods budgeting mechanism where agents
determine both the total volume of expanses and the specific allocation. It is
constructed as a modification of VCG to a less typical environment, namely
where we do not assume quasi-linear utilities nor direct revelation. We further
show that under plausible assumptions it satisfies strategy-proofness in
strictly dominant strategies, and consequently implements the social optimum as
a Coalition Proof Nash Equilibrium. A primary (albeit not an exclusive)
motivation of our model is Participatory Budgeting, where members of a
community collectively decide the spending policy of public tax dollars. While
incentives alignment in our mechanism, as in classic VCG, is achieved via
individual payments we charge from agents, in a PB context that seems
unreasonable. Our second main result thus provides that, under further
specifications relevant in that context, these payments will vanish in large
populations. In the last section we expand the mechanism's definition to a
class of mechanisms in which the designer can prioritize certain outcomes she
sees as desirable. In particular we give the example of favoring equitable
(egalitarian) allocations.
