The paper explores in some detail the semantics of the verbs which Fillmore classifies as 'commercial transaction' verbs: BUY, SELL, CHARGE, PAY, SPEND and COST. It shares Fillmore's belief that these meanings must be defined in terms of general semantic frames, but (like Lawler) it argues that more than one such frame is involved. In addition to the frame for Commercial transaction we need to invoke Trading, Consuming, Using, Giving and Getting, which interact to define the meanings of these verbs (and of course many others). The analysis is formalised in terms of Word Grammar theory, and assumes that each 'frame' is a concept represented as a node in a network of relations. The paper also considers the theoretical status of semantic relations (especially participant roles), and shows that these can be defined within the analysis through the network. One relation may be defined in terms of another either by being an example (in the 'isa' relation) of the other, or by sharing the same terms as the other.