I don't think the math adds up with that price, the price of gold per ounce (or per 28.3 grams) minimum from 2015 forward was around $1,300 (not including this year) so that means those coins are around 1/5th of an ounce (or 5.7 grams)... Unless this manga was made in 2001 which is still hard to believe because gold was still around $400 and ounce then, making the coins 1/2 of an ounce (or 14.1) grams.
Edit : Gold was $1,300 an ounce from 2010 onwards also, but 2011-2013 had gold at around $1,800 an ounce