@luke, I'm afraid the question of purpose and existance is not so simple.
In the Uk for instance, the government tends to farm out a lot of services to charity organizations, at a reduced cost to themselves. This means there are a lot of charities who function as service companies with government grants but get away with recieving public donations too because they are "charities" despite the fact tht they function as businesses, and likewise a lot of actual charities who cannot get! government support because their contract so to speak has been bought out by someone else.
for example, the government is cutting back on providing actual nhs nurses and the like for the eldily by farming out those contracts to "care charities" which has resulted in lots of scandles.
this is my issue with a lot of the structure in th the Rnib. They function as a business, despite appealing for charity donations, they engage in cost cutting measures often to the detriment of their members, they even (rather amusingly), got into hot water because they made most of their blind workers redundent (and of course the board of directors don't have any actual Vi members do they), also as I've said before their focus on wills and legacy donations is frankly scary!
So, on a specific goal orientation, even for a supposedly charitable organization you cannot make any sort of judgements.
also, with big organizations, there are often individual departments or objectives which get reached due to the efficiency of that specific department.
for example, the Rnib's political Lobbying has had some distinct achievements which, despite my dislike of so much else the Rnib does cannot be denied. One recent example was making certain that under the governments new revision of the disability bennifits system, blind people would not be denied the mobility component of disability bennifit, something they were up until 2009, (it always amused me that someone in a wheel chair with an adapted car could have less movement costs than a blind person who must use public transport, yet got three times as much money each week as a mobility component of their disability payment).
In evaluating the Rnib, it is just not clear to me that you can say one thing, some of their departments and goals are well achieved, others, particularly as regards attitude are not.
Of course, other organizations with a single purpose are much easier to deal with. For instance, I've often spoken my admiration for the guide dog association, because they are intrinsically very good at what they do, providing mobility training and, when they assess a person as capable, a guide dog. They have a few ansiliary functions, such as a rather fun holiday service, but their main function they do very well (interestingly enough without! any government recognition).
Myself, I would suggest a slightly different method of evluation, not evaluating the hole organization on simply a purpose function approach as though it were a machine, but defigning a set of purposive goals which a given organization has, devided into the catagories of personal, political, and idiological.
With the Rnib, i'd say idiologically they fail, but politically they often succeed, while personally they can be patchy at best depending upon which department one deals with and who you speak to.
this also as you will notice misses the idea of finance, since though organizations might function as business, the intrinsic difference betwene a business and a charity is that a business exists for it's own sake, a charity for that of others. Since organizations for the blind exists "for the blind" they cannot be judged on a business model, and indeed often such practices impaire their primary function.
thus, I don't see this as an economic or financial matter accept as the financial consequences impact upon the catagorical consequences mentioned above.
With our dreaming and singing, Ceaseless and sorrowless we! The glory about us clinging Of the glorious futures we see,
Our souls with high music ringing; O men! It must ever be
That we dwell in our dreaming and singing, A little apart from ye. (Arthur O'Shaughnessy 1873.)