Sanctions after 20 million, why?

"The US sanctions can affect third parties, such as Russia or one of its companies, if their investment in Iran is more than 20 million dollars.

More at:

http://www.energy-daily.com/reports/Lukoil_to_continue_in_Iran_despite_sanctions_problems_999.html

What sort of sanctions is that? My argument for sanctions on the Seyyeds, is that they are sanctioning the ordinary real secular modern Iranians, who do not like the Seyyed dogma. So the Seyyeds who control the government sector, should be fully sanctioned, and not limited to any sum over US $20 million. The US is not doing enough. It's a cop out.