The trickster in "Dusk" seems to be a sort of apprentice or beginner at his chosen profession. Gortsby listens to his elaborate hard-luck story and then exposes him as a fraud with a single sentence:
"Of course," said Gortsby slowly, "the weak point of your story is that you can't produce the soap."
Obviously this is only a temporary setback. The trickster has learned a valuable lesson. In the future he will simply carry a cake of soap in his pocket. If he perfects his body language and his story, as he is bound to do, he could be earning a pound a day and only working for an hour or two around dusk. This would add up to over three hundred pounds a year, which was a good income for a single man around the beginning of the twentieth century. The typical annual salary of clerks was a pound a week, or fifty-two pounds a year, and many clerks were supporting families on those wages.
The trickster in "The Umbrella Man," on the other hand, is living in the fast lane, so to speak. He is risking arrest every time he steals an umbrella, and he is jeopardizing his health by two things: (1) drinking all that straight whiskey, and (2) doing all that running around in the rain. Furthermore, he can only operate when it is raining, and though it rains a lot in England he has to sell his "hot" umbrellas on days when a lot of people will be caught without protection because of an unforeseen storm.
It does not seem very difficult to sell an umbrella worth twenty pounds for one pound, especially to a person who is caught in a downpour. So I would have to say that the young trickster in "Dusk" will be far more successful than the elderly umbrella man in the long term.
What makes the young trickster's story so effective in "Dusk" is that he has memorized such a complicated scenario. It is hard to follow the story and to understand what the "frammis" is--i.e., what he is after. He was going to stay at one hotel, but that hotel was torn down. He was taken by taxi to a second hotel, but he couldn't find the building again after he went out to buy a cake of soap. Now he needs enough to rent a room at yet a third hotel because he can't get back into the second hotel where he left his money.
Perhaps the purpose of such an involved tale is to keep the listener confused and guessing. The young trickster doesn't want anyone to give him money; he only needs a loan which he will gladly repay as soon as he can find the second hotel where all his belongings are. But what it comes down to is that he wants money.
In addition to pointing out that he couldn't produce the bar of soap, Gortsby might also have asked the trickster why he didn't just go to a hotel and ask if they would let him write a "counter check" or pay the next day. Modern checks are processed electronically, but in Saki's time a check was just a blank form which would serve as a draft on whatever bank was specified in handwriting. If the young man came from out of town, he ought to have had a bank account in his hometown. Banks did not differentiate between checking accounts and savings accounts.
Hotels did not customarily charge for rooms in advance in those days, although the clerk might ask for payment in advance if the tenant had no luggage. Dealing directly with hotel clerks would seem more sensible than soliciting complete strangers on park benches if the young man was telling the truth. After all, it would be the hotel that would end up with the money, so why not ask the hotel to trust him?