I think the article is a bit misleading. Quoted exchange rate in the article was traded in unofficial markets. I've just checked exchange rate for official rate of USD/IRR on several websites (www.forexticket.co.uk, www.oanda.com). All of them show the same current exchange rate around 12,28 Iranian Rial per USD Dollar and this exchange rate is pretty stable since February 2012.
Of course unofficial markets are reflecting the results of the current sanctions and economic sabotage by US. Still, Central Bank of Iran is preserving stable exchange rate to control economic situation, and not to give up for US pressure.
Try actually buying 1US$ for 12.28 rials, you might be in for a surprise.