When mandatory seat belts make crashes safer for drivers, drivers respond to the reduced personal risk by driving more aggressively, which raises danger to pedestrians and cyclists. The safety benefit per accident is partly offset by an increase in the number and recklessness of accidents.
In free-entry equilibrium, if one option were better than another after all costs, people would switch until the advantage disappears, so comparable options end up equally attractive at the margin. This implies that cleaning the air or improving a neighborhood often leaves residents no better off, because the gain gets capitalized into higher rents or prices.
Landsburg argues Iowa grows cars: farmers plant wheat, ship it across the Pacific, and cars come back, so trade is literally a technology for converting grain into automobiles. By this logic, blocking imports to 'save' domestic auto jobs is identical to banning a cheaper production method, destroying wealth rather than protecting it.
The obvious answer (a captive-audience monopoly) is wrong, because a monopolist on tickets could just raise ticket prices instead. High concession prices actually work as price discrimination, charging heavy snackers (who value the experience more) more without deterring light users who still buy a ticket.
A policy is good if the dollar value of its benefits exceeds the dollar value of its costs across all affected people, regardless of who gains or loses, because gainers could in principle compensate losers. On this standard most taxes are 'bad' since they drive a wedge between buyers' and sellers' valuations, destroying mutually beneficial trades that would otherwise occur.