According to French media nearly 150 heads of state and government are attending COP21 along with their estimated 2,000 aides and advisors. They’re expected to pay their own way to Paris, as are 3,000 journalists, 14,000 representatives from non-governmental organizations and another 10,000 miscellaneous national, business, and scientific delegates.

But assembling, securing, feeding, and transporting all those people falls on the organizers and host government. The COP21 host site’s FAQ page is cagey on how much the 12-day event is costing to mount. One frequently asked question is “How much is COP21 going to cost?”—but the linked reply offers no figure.

Other estimates however have put the cost at above €187million (C$265 million, US$189 million). That may have risen with additional security measures taken in the wake of the Nov. 13 attacks on several popular Paris night spots. According to France’s Interior Ministry, 120,000 security personal are mobilized across the country. City officials have also laid on 200 electric cars and chauffeurs for VIPs and declared a moratorium on transit fares, in part to mollify citizens inconvenienced by the climate summit’s impact on daily life.
The United Nations organization responsible for mounting the Paris summit makes no secret of its search for corporate sponsors to help with those costs, but does not reveal how much they may be contributing. However, a U.S.-based corporate watchdog group accuses organizers as well as national delegations of granting sponsoring corporations privileged access.  

Writes Corporate Accountability International in Fueling the Fire: The corporate sponsors bankrolling COP21: “Emissions-intensive corporations from around the world have been granted observer status inside the meetings through their trade associations, and some major industrial polluters and business lobbies will even claim a formidable presence within delegations of national governments themselves.”
Among other corporations investing in the summit, the group notes, BNP Paribas has holdings in Canadian tar sands/oil sands production, and Engie, previously known as GDF Suez, is heavily involved in gas fracking.