It seems quite simple under framework of free market, when there are no taxes or subsidies,price celling or price floors, etc, that can mess up the market: if there is profit (or will be, according to forecast of expert), then wealth was created (or will be created). If profit is negative (i.e. we have loses) then wealth was destroyed.
But what if we have public goods provided by the State? There will be no profit, so this metric is dead in this case. Normally people don't buy things from the State, they are taxed.
Using opinion of an expert seems too fragile strategy to see if wealth is created or destroyed. Probably we could survey people with questions like "How much would you contribute to additional street lighting if there was crowdfunding campaign?", but I'm not sure if it's how it is done in practice.(Please confirm if I right). Ideally it would give us demand curve.