The set-up cost to build "The Big Bus" vehicle was around $250,000. This comes out to around one million dollars in 2022 adjusted for inflation.
For the big arrival of the big bus, a bus station in downtown Los Angeles had to have its roof raised, so the gigantic coach could enter the facility.
The Big Bus was actually two separate vehicles that could be driven separately (as seen before the closing credits).
The bus was actually two International trucks, and the body was a two-part fiberglass shell connected by 500 bolts, each bolt weighing one pound. The four rear wheels were each five feet in height and weighing 1,100 pounds. For the close-ups in the cliff scene, a dummy cab on hydraulic jacks was posed against a rear projection view of Grand Coulee Dam, and for the long shots the actual 75-ton Cyclops bus was hung over an actual cliff by a 125-ton crane. Two drivers were needed, one up front and one at the back connected to the front driver by a telephone hookup.
According to an article in the now discontinued bus magazine "Bus World", in 1976, this movie's actual big bus made a real-life trip in California from Los Angeles to San Diego to promote this movie.