They say precious metals are a hedge against inflation, and yes, I can see that, but the way gold has gone up, along with silver, and platinum, they aren't a hedge against inflation, they're a speculation asset no different that buying stocks and bonds.
To use your graphic, average home in 1970 was around $26K, 721 ounces of gold, in today's prices that 721 ounces of gold is about $2.5M. Average house today is like what, $450K? That math doesn't check out to reflect reality.
Wise words... Metals, like many commodity and other investments, have been used as hedges but that doesn't mean they are infallible. Gold markets are subject to volatility. I used to play in metals contracts regularly back when I managed a manufacturing company that bought gold (and other metals) several 400 oz bricks at a time.
Real estate markets are fickle as well. A family member bought a house in the 70s for around $60K - it needed some work but was a great beach location I enjoyed when I was a kid. Just looked at Zillow and its worth $8 million today so a great long term investment had they kept it for 50+ years. Better performing asset than gold in this case.