From science fiction great Frederik Pohl's ongoing blog/memoir "The Way the Future Blogs," a lovely post explaining how Pohl became a "literary agent" in the era of the science fiction pulps, inspired by the desire to save 8¢ per story in postage.
As I had learned from my study of Writers Digest, I could mail in my stories — and had done so. The catch to that was that I was required to enclose postage for the return trip in the (likely) event of rejection. That had amounted, in the last story I had submitted by mail, to 9¢ in stamps each way, total 18¢. While the cost, if I delivered them in person, would be only a nickel each way for the subway. (Plus, of course, whatever price could be put on my time for the 45 minutes each way it would take for me to do it — but, then, nobody else was offering to buy any of my time at any price.)
That represented a nearly 50-percent reduction in my cost of doing business, or even more — much, much more! — if I had enough stories to submit to make a continuing process out of it. I could, say, take the subway to editor A's office to pick up rejected story X and at the same time submit new story Y, then walk (no cost for walking) to the office of editor B to try story X on him. And there was no reason for me to limit myself to a single story each way at each office.
The only thing that could prevent me from working at that much greater volume was that I hadn' t written enough stories to make such economies of scale pay off, and that, boys and girls, is how I became a literary agent.
I read a lot of memoirs from this era of the field when I was starting out, and always felt cheated by the immediacy of the pulp writer experience. Writers would post stories to editors, hear back right away, send their stories out to new editors.
I entered the field in the mid-1980s, when you'd send a "disposable manuscript" (laser prints only, no dot-matrix!), to an editor along with a SASE (for Canadians, this meant lining up at the post awful for expensive International Reply Postage Coupons), and then wait. And wait. It wasn't uncommon for publishers to take 18 months or more to send out a simple form rejection. And of course, the rates had barely changed since Pohl's day, losing so much ground to inflation that the sums involved had really become tokens.
On the other hand, in those days, the editors of the major sf magazines were fielding more than 1,000 unsolicited manuscripts per month, for four or five uncommissioned monthly slots in their publications, so there wasn't really any good reason to pay more, or hire more staff to reject stories faster.
It took ten years for me to sell a story to a "major" market, and during that time, I racked up hundreds of rejections. Looking back on it, I can't really understand why I kept on, except that I couldn't stop. I'm glad I kept at it, but man, what a grind that was.