Haggling over the price of a concert ticket usually requires sending several plaintive e-mails to a Craigslist poster. But a La Cañada company wants to complete the haggling with a few simple mouse clicks. Zigabid.com, which launches today in public beta testing, says it is the only ticket-vending site that lets buyers and sellers bargain over prices for tickets to concerts, sports matches and other events, all using a simple interface that allows for direct buyer-seller communication. Although Zigabid's current inventory consists mostly of resale tickets from individuals and brokers, the company hopes to become a player in the primary ticketing market. That would mean taking on Ticketmaster and turning tickets into traded commodities. The negotiation-based approach could help sell more tickets, if at lower prices, which runs counter to the music industry trend of soaring concert ticket prices.