At the time when Jesus gave what we call the Sermon on Mount, which you can read in Matthew 5-7, He might well have meant exactly what He said when He said these words! If you know anything about the historical context of the times in which Jesus lived, you might have a better understanding of why Jesus said what He did. While it is almost universally understood that Jesus was speaking parabolically here, it should be clear from this context that Jesus was not simply using 'poor' as a metaphor for the meek & humble ones that followed the Messiah!
'Poor', particular in this day & age most often, probably, has reference to those have monetary troubles, although these often think of themselves as being the truly 'rich' ones! Although someone that barely brings in enough money to cover the necessities may be thought of as being 'poor', this adjective might also be used in a derogatory, almost metaphorical sense, as in, 'what a poor excuse for a human being'! On a side note, these 'poor' ones are often some of the richest, in monetary terms, at least, people you'd ever meet!
'Poor' can also be a qualitative statement as well, as, 'that's a poor example' ( or specimen ), meaning that particular model. There may be a defect in the entire 'batch', and so you might say that it was 'poorly made', and in the case of those who have to sort out products on an assembly line, certain examples might be so defective or lacking that you might say they were 'too poor to make the grade'!
In the Scriptures, though, the term is often used, both metaphorically & plainly, to describe those who were meek & humble, as well as those who were monetarily destitute, as opposed to those who had plenty of money! Often, as we observe in today's society, as well, it is often, though not always, the case that those who have plenty of money are rather 'poor' while those who may have to struggle to put food on the table are truly 'richer' than most!
While we most often see the term 'poor' in Scripture used of those who are monetarily lacking, even this usage is often parabolic or metaphorical! We are told, in various places, that we are not to prejudiced to the rich over the poor, or the poor over the rich. Is is a well-known fact, among most anyway, when Jesus uses the opposite moniker ( 'rich' ), as in, 'it is hard for a rich man to enter the Kingdom of Heaven' ( Matthew 19:23 ), that He was speaking metaphorically against the Pharisees, who trusted in their own righteousness rather than seeking after that which Jesus symbolized!
From the above, we may ascertain that many of the 'poor' that we read about in Scripture, particularly in Jesus' day, were those who were meek & humble enough to accept Jesus as their Messiah! As mentioned, and could no doubt be ascertained from even a cursory study of the Life & Times of Jesus, those who did accept Jesus as the Messiah were put out of the synagogues, and being Jews themselves, for the most part, were shunned by the majority, both in fellowship & business!
Therefore, although we may traditionally understand this saying of Jesus in the Battitudes as referring to those with a meek & humble spirit, we may well interpret Jesus' words in the plainest sense! The poor man in Jesus' day was very often the common man, who eked out whatever living he could, while the rich ones were usually the scribes, Pharisees or Saducees, the religious leaders of the day. Those who collected the taxes for the Empire were rich or poor, according to how well they did their job!
The 'poor in spirit', then, though they were often truly lacking in material wealth, were those humble ones who were able to see that Jesus was the long-awaited Messiah of Israel! When these 'poor in spirit' did accept Jesus as their Messiah, despite knowing they would be despised & rejected of men, they received an extreme blessing, ome that was eternal in the heavens!
Charles Haddon Shank