Like I said in my post, a lot depends upon when you by and sell. If you brought at the 1980 high and sold today, you would have lost well over 50% of your investment. If you brough at the low in 2000 and sold today you would have made about a 46% return on the principle investment, although the actual return would be lower after deducting the super high commissions normally charge by commodity brokers.
I forgot to add, that the gold you purchased probably has intrinsic value beyond the mere value of gold bullion.