negotiation. Only an accepted offer is firm and fixed. And usually only when it is prefaced by the terms: Best and Final. Your 'counteroffer' as is was, instructed Coz to ship on his quote albeit which was in error; however it is obvious he thought his quote was the book retail, and that's what he did. Your changing his numbers does not make it his quote. Were this a public procurement process, the entire transaction would be canceled and re-bid. The award would never be made on the basis of a mistake like this.
BTW if the court of public opinion were to be convened for the purpose of rendering an opinion about Coz as a retailer to the Z community, they would offer an excellent opinion thereof. gordo