Much of the cost increase in flying training is regulatory cost and airways charges. Prior to 1987 there were no airways or airport charges, flying for free.
And the regulatory burden and cost since the early 1990s (from CAA to CASA) has grown very significantly, in inverse proportion to its usefulness and safety benefit. I haven't costed the regulatory and airways cost over the past 50 years (since the days of DCA), but in sum I suspect regulatory and airways costs amount to at least 40% of CPL training cost.