In 2006, The Theatre Trust estimated that £250 million would be needed by 2018 to maintain the West End's historic theatres, most of which are over 100 years old.  This equated to £17 million per year at contemporary prices.  Cameron Mackintosh pledged £40 million towards maintenance. In 2003, the Theatre Trusts report Act Now! reported that 40% of auditoriums had poor public circulation and 24% had inadequate or non-existent air-changing systems.
Paying to the gallery, Arts Industry , 19 May 2006

Equity estimated real cost increases in UK theatre of 52% between 1997 and 2007.
A Brighter Future: The case for investing in subsidised theatre, Equity, 2007