If we're talking Colorado City, according to Krakauer in 'Under the Banner of Heaven', only the first wife is legal. The rest are legally 'single mothers' so qualify for welfare benefits. That's where a huge portion of the money comes from. As I recall, Krakauer actually has $$ figures on how much welfare goes into Colorado City.
No problem with group marriages from my point of view. The problem in this instance is not so much the group marriage as the fact that arises from brainwashing thru religious authoritarianism. Children are pulled into it before they have a chance to think for themselves. I wouldn't see it as a problem if their kids were required to grow up, leave the town, go to college, experience the world, then come back and see if they want to hook up with some ugly fat, perverted authoritarian bastard. If they do it under the those circumstances, there's no one to blame but themselves.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13