From G.A. Cohen's Self-Ownership, Freedom, and Equality:

Begin by imagining a society without money, in which courses of action available to people, courses they are free to follow without interference, are laid down by the law. The law says what each sort of person, or even each particular person, may and may not do without interference, and each person is issued with a set of tickets detailing what she is allowed to do. So I may have a ticket saying that I am free to plough this piece of land, another one saying that I am free to go to that opera, or to walk across that field, while you have different tickets, with different freedoms inscribed on them.

Imagine, now, that the structure of the options written on the tickets is more complex. Each ticket lays out a disjunction of conjunctions of courses of action that I may perform. I may do A and B and C and D OR B and C and D and E OR E and F and G and A, and so on. If I try to do something not licensed by my tickets or ticket, armed force intervenes.

By hypothesis, these tickets say what my freedoms (and, consequently, my unfreedoms) are. But a sum of money is nothing but a highly generalized form of such a ticket. A sum of money is a licence to perform a disjunction of conjunctions of actions - actions like, for example, visiting one's sister in Bristol, or taking home, and wearing, the sweater on the counter at Selfridge's.

Suppose that someone is too poor to visit her sister in Bristol. She cannot save, from week to week, enough to buy her way there. Then, as far as her freedom is concerned, this is equivalent to 'trip to Bristol' not being written on someone's ticket in the imagined non-monetary economy. The woman I have described has the capacity to go to Bristol. She can board the underground and approach the barrier which she must cross to reach the train. But she will be physically prevented from passing through it, or physically ejected from the train, or, in the other example, she will be physically stopped outside Selfridge's and the sweater will be removed. The only way that she will not be prevented from getting and using such things is by offering money for them.

It isn't money per se, it's the self-determination that money permits. Those who don't have it are told that they're merely 'unfortunate,' rather than the victims of social relations of constraint they actually are, and so the appropriate response of violent anger is replaced by depression and self-loathing.