The paper's single reported own-price (marginal price) elasticity is its headline empirical result; the text states it explicitly. || "Marginal price is significant at .01 and of the expected sign. Marginal price elasticity at the mean consumption rate is -.28." (p.358, Table 1 discussion)
Houston, D. A. (1982): “Revenue Effects from Changes in A Declining Block Pricing Structure.” Land Economics 58(3), 351-336