This
http://www.staffordshirenewsletter....tners-Ludlow/story-24737351-detail/story.html has to be the way forwards. Sharing the performance, and the cost of production, with other venues (providing they are not too close to each other, could benefit all parties.
Then Stafford could reduce the length of its Shakespeare run and use the stage and seating to provide other attractions. For example, it could expand the current music festival
http://www.staffordbc.gov.uk/liveatthecastle into more of a nationally attractive small music festival. Or comedy, literature, science, film, other theatre, carnival etc. and appeal to a wider range of people, spreading the cost of setting up and maintaining the venue, whilst retaining the core Shakespeare Festival.
They could even try and be crafty; A number of years ago, I lived in Weymouth for 5 years. The local council realised it couldn't afford to provide the regular firework displays that were attractive to locals and visitors. So it announced it was going to hold an international fireworks competition and invited countries to enter. The result was that the town was able to have a 'free' firework display every week through the summer months (even China put in an entry).
The trick is to use the venue for a wide variety of events each year, some will be attractive enough to maintain as regular annual events, others might need to be rotated to keep them fresh.
It's not rocket science; unless you hold a science festival.