Its crazy, i would say you could be touching 30k+ depending on your install.
3 projectors with motorised screens, a matrix unit and all new cabling is around 8-10K.
Sound and lighting is crazy money, I was looking at some DMX controlled movers. They range from ?200 up to over a 1K per light.
We were tempted to try the install ourselves, but there are too many factors to consider. (beam spread, lumens etc) if you wire the lights too close to the audio you'll get hum and other interference issues.
You also need to make sure your audio and video gear are on the same ground, or you will get ground loop that will cause noise/buzzing when everything is plugged in.
Going by previous productions in our school we would need a sound desk in the range of 3-5K, DMX patch in points in multiple locations around our Hall. As well as patch locations for a digital snake.
Our big issue is that our desk setup moves depending on the show and how many people the hall is setup for.