Throwing Away Papa's Money

The Gemara (סנהדרין כב, ב. נדרים נא, א) tells us of a certain "Ben Eleasa" who would spend large sums of money in an effort to learn the unique hairstyle that the Kohen Gadol had in the Beis Hamikdash. The Gemara comments that this effort was "not for naught."
Why would the Gemara feel it necessary to inform the reader that it wasn't for naught - what would prompt one to think that it was?
The Maharsh"a explains: Let us examine this man's name - "Ben Eleasa." Why was he given this name; if he was indeed a wealthy and important man, why did he not merit to be addressed with his own given name? The answer is that this man did not accumulate his own wealth, rather he inherited it from his father. As such, his entire legacy was attributed to the owner of his money - his father.
Now, people in such a position usually squander their money as they do not appreciate its value. Therefore, the Gemara tells us that this man did not do that; "not for naught" did he expend large sums of money, for his motives were noble, as he was trying to learn about the ways of the Kohen Gadol.
מהרש"א חדא"ג נדרים נא, א ד"ה מאי בן אלעשה

Status Switch

The kohen enjoys an elite status even today. He is called up to the Torah first, he gives the special brachah of birchas kohanim, and enjoys other privileges as well. In the times of the Beis Hamikdash, the kohen was most certainly special as he was privileged with the holy task of the daily service.
The levi'im too were special, as they were charged with the job of singing in the Beis Hamidash, but they don't compare to their elite brethren.
Kayin was the first born son; after him came Hevel. Kaballah explains that Kayin was conceived in sin, and as such, the privilege of kehunah was taken away from the first-born and given to the kohen. It is explained further that the levi shares the same spiritual components as the first-born.
Thus, when Moshiach comes, things will change. At that time, the sin of Kayin will be purged, and so, the kohanim will be downgraded to the status of levi'im and the levi'im (representative of the first-born) will be upgraded to their rightful status of kohanim.
לקוטי תורה מהאריז"ל יחזקאל
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Timeless Wisdom

The Rishonim took great efforts to explain the reasons and the beauty behind the mitzvos Hashem gave us. In the forefront stands the Chinuch who authored a book compiling all the 613 mitzvos in a clear and concise format. The author is generally assumed to be R. Aharon Halevy, or the Re'ah, of mid thirteenth century Barcelona. In the entry he authored for every article, the Chinuch gives a brief paragraph explaining the "shorshei," or the "depth" of the mitzvah.
At times, they are quite timeless:
Regarding the mitzvah on the Leviim not to encroach on the Kohen's service and vice versa, the Chinuch writes:
"...The tasks of these two groups are precious and sacred; as such, care must be taken lest they become subject to idleness and neglect. There is no doubt that a job charged to two people or more will be subject to more neglect than a job charged to but one man alone. For many times each one will rely on the other; meanwhile, the job will not get done. This is clear to all men. Indeed, our Rabbis succinctly expressed this very point: 'The pot of two partners neither heats up nor cools down...'"
ספר החינוך מצוה שפ"ט