I thought that it might be a good idea to mention the events surrounding R. Yohanan and Ilfa. There is a lot to learn from that event but it seems to me that I was more in the shoes of Ilfa than R. Yohanan.
Nowadays the kind of test that Ilfa faced seems to have morphed . Certainly "parnasa" [livelihood] is a test and always has been, but today there are more kinds of things which draw one away from Torah. Mainly they are along the lines of, "Sure learning Torah is a good thing, but come and do this more important mitzvah that is even greater than learning Torah." Or "Come do this mitzvah so that your Torah will be more real and authentic and even better." There are countless of ways for the evil inclination to seduce one away from Torah. After all all the Satan has to do all day is think up new ways to draw people from Torah and make up deep sounding teachings that seem to imply how other things are better than Torah and then inspire his agents with these deep lessons.

The basic events were as follows. R Yohanan and Ilfa were sitting and learning Torah. דחק להם שעתא. The hour pressed upon them. (That is: they were starving yeshiva students.) They discussed going out for סחורה (to work). They were sitting near a stone wall. R. Yohanan heard two angels discussing whether to topple and push down the wall on top of them. One angel said "Let's push this wall down on them since they are thinking of leaving learning Torah to do business." The other angel answered "No. Let's leave them alone because for one of them עומדת שעתא the hour stands. (i.e. one of them will still continue to sit and learn)." Ilfa went out and became a business man. In the meantime R Yohanan continued to learn Torah and eventually became the Rosh Yeshiva (head of the yeshiva).
When Ilfa returned from one business trip he encountered R Yohanan and tried to show that he was still learning Torah even while doing business. He said, "Show me anything in the Tosephta  and  I will show you were it is hinted at in the Mishna."  Then the Gemara brings that legal discussion.

The implications of these events are vast and few people are willing to heed the lessons. There is not question that what Ilfa did was perfectly justified. Still we see there is some level of appreciation of Torah that R Yohanan must had had. That is sometimes the real test is not whether you are sitting and learning. It is rather, "Do you appreciate the Torah enough? Or are you willing to give it up for a few bucks?"

My own appreciation of Torah was reinforced by a small book בניין עולם  which brings the Gra on the Mishna in Peah who brings the Yerushalmi. A very important aspect of that discussion is the question "What is the minimum amount of a mitzvah or a sin?" This comes up concerning  לא ירבה לו סוס and שריטה and קרחה.(note 1)

There is a lot to go into about this but the basic idea is that the Yerushalmi says even one word of learning Torah is worth more than all the other mitzvot.

But the Mishna not not say that learning Torah has an infinitesimal measure. Rather "No measure." Thus it is like שריטה that one would get one set lashes for lots of שריטות because it has no שיעור. This is different from things that have  a שיעור  like קרחה. Thus for קרחה one gets five sets of lashes even though there was only one התראה issued--because it has a שיעור.
There is much to think about here but in short it is not as if every word of Torah is a separate mitzvah. Rather is one sits an learns for example a whole day in the Mir Yeshiva in NY or Chaim Berlin, then he gets a  big mitzvah. That is the same as if he did lots of שריטות. He gets one big sin. It is not as if he did lots of little sins. So with Torah that has no minimum measure, sitting and learning a whole day is a big mitzvah, not lots of small mitzvot.

I should mention that people that use Torah to make money are generally enemies of those that learn Torah for its own sake. So the fact that people are sitting and learning does not make them friends to Authentic Torah. For all we know they might be doing it for the money and ease of life style and to get out of the IDF  and the prestige. In fact to get out of the IDF was the one main motivating factor is the formation of 99% of all Israel yeshivas.
This is the trouble with the religious system. It is a breeding ground for anti Torah and anti Israel zealots. The fact that people learn Torah all day says nothing about their integrity or true purpose. if fact 99% are in it for the ease and comfort of lifestyle of sitting and chatting all day and getting paid to do so.

With the exception of Ponovitch and its off shoots most yeshivas there have no interest in Torah at all.

No lower measure  also means as it does for peah--that one fulfills it with an infinitesimal amount.that one fulfills the mitzvah by saying one word of Torah.

(note 1) If one does many scratches  שריטות there is one set of lashes. But for קרחה even with just one warning there are five sets. The reason שריטה has no שיעור.

the idea of minimum measure comes up in truma and maaser. if one gives less than 10% it has not the legal category of maaser. the rambam writes the same about truma in laws of truma ch 3 halach 6 and 7. the trouble is halacha 6 where it is truma and it is unclear what the difference is--unless you go to the Yerushalmi. there it is clear the difference is if one intend to take more truma or not. Rav Shach explains the Rambam thus: If his intention is to take more then it does not have the category of truma at all. If not it is truma. That is the opposite of how the Rash [rabainu Shimshon explains the yerushalmi.]