Each peacekeeper costs about $51,000 a year. The money comes from the wealthier countries, which the UN solicits to pay for these operations. Most of the troops come from less wealthy nations, where the troops are happy to serve for about a thousand dollars a month. This is usually much more than the troops normally make. There's also some new equipment they will likely get, again, paid for by wealthier countries. The troops also get to travel. OK, not to a tourist spot, but usually to an exotic, and somewhat dangerous, one. The wealthier nations don't like to send their own troops, because such missions are not politically popular. Sometimes they do anyway, but the politicians pay the price, and often pull the plug on the effort if it causes too much negative feedback from the voters.
The hat is being passed again, as over two billion dollars more will be needed to pay for the additional peacekeepers. Actually, not all the peacekeepers are soldiers. Each peacekeeper force is about 10-15 percent police, and a similar percentage of civilian staff. Raising additional money may be easier than getting the people. Only a few nations provide reliable troops, and they are reluctant to provide more. Going to other nations, with less capable soldiers, is asking for trouble. In the past, the lower quality soldiers have caused all sort of problems, from inability to deal with the local bad guys, to simply becoming another bunch of bad guys.
The UN would like to establish a small (about three thousand) force of full time peacekeeper specialists, that can supervise peacekeeping operations, and provide professional assistance to the large number of operations underway. Currently, this vast operations is handled with something of an improvised management setup. Most UN peacekeeping missions have failed, but the UN has managed to put a positive spin on these failures. People want to believe that peacekeepers succeed, and the UN plays on that. It's a living.
The growing demand for UN peacekeepers is expected to mean that over 140,000 may be in service by the end of 2007. Currently, there are 93,000, serving in 18 different operations. The Lebanon and Darfur operations will require at least 15,000 each. There are larger operations underway right now, with 21,000 in Congo and 17,000 on the Ethiopia-Eritrea border.