A new 1971 Subaru FF-1G was $2,500.
A new 1984 VW Scirocco was $11,006.
IIRC, wife's new 2008 Audi A3 was $30K.
Sorry, but using new car costs, I'm only seeing "12x" growth across 37 years, and only ~3x growth for the period of circa 1983 to present.
And sure, car prices have gone up over time, but so too have the content. I don't recall having airbags, ABS or traction control in my '84 VW and my '71 Subaru didn't even have air conditioning ... nor even an automatic engine choke, for that matter.
From a scuba analogy, these cars were akin to the 'Mae West' horsecollar that lacked a power inflator, with its viciously endearing 3/4" wide crotch strap. Hurray for modern technologies...but let's remember to pay for them too.
Not really. The modern class typically today is arguably around $300 and the 4-5 of them that you need for comprehensive content equivalancy means that you're in the $1200-$1500 range, which pretty much matches your 15x claimed cost growth value. OTOH, if we use the cost growth numbers that I listed above, then today's products are at least 4x higher than what is explained by mere inflation.
Shifting inflation benchmarks, in 1983, the price for a gallon of gasoline was 81 cents. Today its roughly 4.5x higher and using that, the $100 class becomes equal to $450 today...which buys probably OW + AOW, but not Rescue, Deep or Deco.
Granted, we really should go to the Government's Consumer Price Index, so using
this tool and the years 1982-2007 (since 2008 isn't available yet), it reports that what cost $100 in 1982 would cost $212.21 in 2007.
Care to list a couple of places where one can get even just an OW class today for $212, including the pool equipment and textbook?
-hh
PS: just for the heck of it, by backing it up to 1960 (IIRC, roughly when PADI was founded), $100 in 1960 would cost $692.89 in 2007. IMO, that's still not enough for four classes today.