Using a new data set of US sportscard conventions, this paper extends and tests the pricing theory of two-sided markets. Since most sportscard conventions are local and convention organizers must set fees to attract both consumers and dealers, we have detailed information on consumer price, dealer price and platform competition. Consistent with the theory, we present two findings: first, consumer pricing decreases with competition at any reasonable distance, but pricing to dealers is insensitive to competition and in longer distance even increases with competition. One consistent explanation is that dealers multi-home within a short distance but single-home across longer distance. Second, when consumer price is zero (and presumably cannot go beyond zero), dealer pricing is more likely to decrease with competition. These two findings confirm a link of pricing between the two sides of the market. * We thank Mark Armstrong for guidance at an early stage, and to John List, Glen Weyl, Julian Wright, and seminar participants at the conference on the Future of Academic Communication at the University of Michigan for advice and comments. David Rapson, Haizhen Lin, Supatcha Mahathaleng and Lauren Moon provided excellent research assistance. All errors are our own.