I'm afraid you would have to beat them at their own game - making relationships with each venue (convince them you will help them sell more tickets, or give them a larger cut).

At its heart its not a technology problem, although you'd have to employ technology to operate cheaper that ticket master. (Which includes preventing bots or scalpers from grabbing all the good tickets for hot shows right after they go on sale).

my 2c

Edit: Perhaps one way around this problem is to provide an easy way for venues to sell their own tickets. Let them setup their own web-front where they can sell will-call or even mailed tickets. Allow for features like will-call ticket transfers. The question is if venues that don't already do this will be convinced to. I'm not sure what is keeping venues like The Fillmore from using any web presense other than Live Nation and TicketMaster. Hopefully its just technophobia, not any actual lock-in...