How Big Can A Tribute Be?

Just seen a couple of tributes listed coming to the O2 Academy in Newcastle, Cash (Johnny Cash) and The Rising (Bruce Springsteen). 

It's only a few years back I was seeing Benwell Floyd at the Archer in Sandyford, but now The Australian Pink Floyd Show (no relation) are the biggest tribute band in the world, lugging along with them Pink Floyd's official light show adapted for the Antipodeans.

With bands like Limehouse Lizzy, Black Rose, Maiden England and Powerage (AC/DC), I wonder how long before one of these outdoes the band that they are paying tribute to!!!