Markxxx your math is wrong.
you do not get 25% increase per year doing the math the way you did. You are not compounding the interst:
$10,000 when purchased
At 25% per year the vaule each year is as follows:
$12,500 year 1
$15,625 year 2
$19,531 year 3
$24,414 year 4
$30,517 year 5
$38,147 year 6
$47,684 year 7
$59.605 year 8
$74.506 year 9
$93,132 year 10
V=P*(1+I/100)^n
V = value now
P = principle
I = interest in %
n = number of compoundings
Sovle for I
I= 100*((V/P)^(1/n)-1)
I in your case is 9.6 % per year which is a pretty fast increase although it was in the mid seventies which had high inflation.
From 1976 to now the increase was 1.9% per year pretty low.