For a graph with edge weight function $c : E \rightarrow Z$, a price query is an assignment of node weights $p : V \rightarrow Z$. Such a query has a yes answer if and only if there is a $(u,v) \in E$ such that $p(u) + p(v) > c(u,v)$. (Intuitively, the $p(v)$ are “prices” on the nodes, the $c(u,v)$ are costs of producing $u$ and $v$, and a price query asks if there is an edge we are willing to “sell” at the prices given by the query.)