If the Bay Area were the entire world, I would agree, but most of the country is very cheap.
http://rt.com/usa/hawaii-one-way-tickets-homeless-824/
Now if only New York will offer airline tickets instead of bus tickets, the homeless can commute back and forth between New York and Hawaii forever. :)
http://www.nytimes.com/2009/07/29/nyregion/29oneway.html
Also, SF has the Homeward Bound program, which is similar: