Collective price reduction has a long and noble history, but maybe it's also a way for people to respond to seemingly endless price rises especially as real wages (but not profits) are barely keeping up. So maybe print some of your own vouchers :
a4 sheet: http://www.stuffit.org/cabotcircus/flyer-bleed-4mm.pdf
and gather some friends and see whether 50% off (or more?) means you can actually afford to take away some of the shiny items on display rather than stare listfully through the windows.
Rumour has it that people are doing this on saturday