This only works if the employers don't see it coming.
In many countries (like mine) organised labour has a wage negotiation-followed-by-industry-wide-strike season. Every year, come rain or shine.
Industry has long responded by:
a) adjusting their 'final price' to accommodate the theatre
b) automating whatever they can
c) scheduling plant maintenance
d) learning which jobs can be eliminated and doing so.
All without paying a cent in wages.
Since they seldom get all this done inside 6 weeks, its takes the labourers years to recover even a 5% increase.
Many (mining, paper, logging, hospitals) even budget for it.