  Accelerator-based high-energy physics have been in the forefront of
scientific discoveries for more than half a century. The accelerator technology
of the colliders has progressed immensely, while the beam energy, luminosity,
facility size, and cost have grown by several orders of magnitude. The method
of colliding beams has not fully exhausted its potential but has slowed down
considerably in its progress. In this paper we derive a simple scaling model
for the cost of large accelerators and colliding beam facilities based on costs
of 17 big facilities which have been either built or carefully estimated.
Although this approach cannot replace an actual cost estimate based on an
engineering design, this parameterization is to indicate a somewhat realistic
cost range for consideration of what future frontier accelerator facilities
might be fiscally realizable.
