It is my understanding that buyers of "fine art" do care about the investment side of their purchase, since ever. Collectioners of past centuries did the same. They "bet" on a certain artist (which they liked) to become famous, or more famous. The obsession for the "unicity" of the work arrived to the point that certain artists (and I think Michelangelo included) would sculpt statues and then "fake" them as ancient ones (by letting them a couple years underground and that kind of stuff) with the exact goal of selling them for more (as archaeology findings). If it is a "modern" work the sculptor (which could have been Michelangelo or whoever) might make another one "as valuable as this one".
If it is an ancient work, a modern sculptor could make a "replica" but it would always be a "replica".
So you get the point. A fine art buyer / collectioner is "by definition" a speculator, when big money is involved. The game here is to gather a collection that posterity will judge great. When you buy a young Caravaggio you don't know (you suspect) that Caravaggio is going to become Caravaggio.
On another level, when you buy a modern painting you know you buy an "unique" copy (only "unique" after the painter dies, but, yes, fairly "unique" even during his life). With modern reproduction tecniques, you can have paintings reproduced in series with all the relief, the thickness of the colour. But such a reproduction will never have the value of the "original".
In photography we have a problem, because the photographic process is "intrinsically" reproductible in unlimited numbers. This makes it intrinsically unfit for the "fine art" market, just as one could not collect, as "fine art", books or teapots however nicely made.
Enter the "limited edition" concept, and there you are, competing for the same wall space with painters!
That obviously implies either that you are already pretty decently famous, or that somebody, liking your work, "bets" on your future. But he can bet only if you create the possibility of the bet by numbering your prints.
Personally I think that declaring a series of 10 is in itself wrong. First it is not likely that you will keep your promise, gives the impression that you yourself don't believe in the saleability of your work after all, and also you will never became famous by selling 10 at a time, because in your lifetime you will produce a certain limited number of works that will make your fame, and those works must circulate, be seen, be talked about. You might declare let's say 100, and the buyer knows that, probably, you will only sell 20 or 30 in your lifetime. But that declaration puts a very important "upper floor" to the series. A print which sold 40, 50 times is maybe more valuable, for a collectioner, than a print which sold only once. The print selling 50 times made some noise, was noticed, appreciated, talked about. But the "upper floor" is important for the art buyer. If the photographer arrives to 100/100 that's very good for the buyer! Provided that now, that your print is famous, and that your bet proved right, the "artist" keeps his promise, rewarding your bet on him.
Now it's the "series" the limiting factor. The print would have sold more, but it's limited. That makes the value of the print. A print selling 100/100 is better than a print going no further than 7/100, in general. (During the lifetime of the photographer. After his passing, and if he is famous, the 7/100 will maybe be worth more).
It is my understanding that in making numbered prints one should always start with a large, very large format print. You declare a series of 100, and there you stop, if you ever reach it.
But you can, later or during the first series, start a smaller series, cheaper, that you declare, let's say, for 500 copies.
That would NOT detract from the value of the larger, more limited series. Actually, if the small print has success in the market, your large print will increase in fame and value. The success of the smaller (more numerous) series will not detract from the value of the "real original big copy, signed and very limited in number".
I'm not that kind of photographer who can ever hope to sell numbered copies. I don't even print. But to me it is evident that by numbering copies the fine-art photographer willing to sell his works is making a service to the buyer and will make his copy really "more valuable" for the buyer.
It goes without saying that the photographer absolutely must respect his promise, or he would be no more than a thief, a conman.