$100 put into S&P 500 in 1975 would be about $7500 today, or about $1250 in 1975 dollars.

$100 put into gold in 1975 would be about $2600 today, or about $440 in 1975 dollars.

S&P 500 would have had 3x the returns of gold.

check your numbers with a purchase date of 1971.