Oh yes it is unfair, but it comes from lack of thinking in a way, I am using arbitrary amounts here of course, but it would be much better for the money to be allocated as a personal allowance for the wife, say $50 per wife, now they all are equal and have equal needs, whether that is to buy certain personal items, get their hair done or save up for some clothes, whatever. Plus then an allowance for each child...in this way, each child has the same amount of money, of which the mother may choose to give a proportion of it over as 'pocket money' to the older kids and the rest would go towards clothing and other expenses. Rather than every wife getting a split equal amount. Think of it this way, if they all had an equal $400 allowance, Mariah might be getting the brand new car and Aspyn might get a second hand bicycle, how is that ever fair?
However, I do feel we are probably letting imaginations go wild on this, so far we really only know about the houses all being split equally four ways, they might dole out money a bit differently. My guess also is that they are paid separately by TLC and so, their situation is vastly different from how it was before 'Sisterwives' came along.