Absolutely fascinating stuff! They even had aeroplanes before I was born!
Since nominal prices are hugely misleading, I looked up the cumulative inflation since November 1967. To get express the data in current prices, you need to multiply by 4.18.
So the AMS-JFK return fare would be 11524 guilders in F and 6734 in Y. Converting to the new-fangled euro, it works out at 5229 and 3056 respectively. Not too bad for F, but pretty exorbitant for Y.
CPH is not as extreme: 956 euros for F and 693 for Y.
LIM would be 9348 euros in F, 6006 in Y.
TYO is almost unimaginably expensive in today's prices: 14,820 euros in F, 8,923 in Y. Again, the F fare is not that totally outrageous given the current walk-up fares on premium airlines, but the Y fare is very far from affordable. In fact incomes have risen faster than inflation, so the relative affordability would make the current-day equivalent fares even higher. Flying certainly wasn't for the masses.