The most basic rule of economics is that of supply and demand. The interaction between these two forces is the key—often the only—factor in determining the price of an object or service. In order to maximize economic efficiency, providing consumers with the goods they want at the lowest possible price, market forces must not be tampered with. Hence, violation of anti-trust laws, which forbid companies from colluding to limit supply or determine pricing and hence increase their profits on the backs of powerless consumers often (though not often enough) carry harsh penalties.
However, economic theory teaches that there are times when regulation i.e., interference with market forces, is needed. There are certain industries in which economic efficiency requires that monopoly status to be given to a company and hence, it is clear that government regulation of pricing is required.
In addition, all countries interfere with a pure market model in order to advance certain social goals. Doing so sparingly and effectively is the key to promoting social values without harming the economic wellbeing of the country.
The Torah system is no different. It, too, mandates times when market forces must give way to even more important goals of social justice. Perhaps most famous are the “boycotts” imposed by Jewish communities when faced with excessive pricing. For example, on the very first page of Hilchot Shabbat, the Mishneh Berurah rules that all—poor and wealthy alike—must forgo the custom of eating fish when fish merchants, recognizing the inelastic demand for fish, raise their prices before Shabbat. Similarly, it was once common—and if I am not mistaken, this is still the case for Gerer chassidim—for communities to limit the maximum price one can pay for a lulav and etrog.
Yet these ordinances pale in comparison to the market intervention ordered by Rabban Shimon ben Gamliel.
The Torah commands that upon the birth of a child, the mother “shall bring a sheep in its first year as a burnt offering, and a young dove or a turtle dove as a sin offering” (Vayikra 12:6); or if she cannot afford to do so, “she shall take two turtle doves or two young doves: one as a burnt offering and one as a sin offering” (Vayikra 12:8).
Seeing an opportunity to make a quick buck, bird merchants raised their prices, so much so that “it happened that the price of birds was a golden dinar” (Keritot 8a). Sadly, it is not uncommon for people to prey on the religious needs of others, at times even more so than in regular commercial transactions, adding a dimension of chilul Hashem to the violation of the laws of ona’ah, price fraud.
Seeing what was happening, Rabbi Shimon ben Gamliel, the Nassi—and hence, leader of the people—declared: “I swear I will not go to bed tonight until [the prices of pigeons will be] a silver dinar.” When one considers that a gold dinar was equal to 25 silver dinarim, one understands the extent of the price gouging and the need for Rabbi Shimon ben Gamliel to act.
He thus “came to the Beit Din and taught: A woman who has five births…brings one korban only” instead of the biblically required five. And having brought this one korban, “she can eat sacrificial meat and is exempt from bringing the sacrifices [for her other children]” (Keritot 8a).
Rabbi Shimon ben Gamliel was, as Rashi explains, violating Torah law. He did so because “There is a time to act for the Lord; they have nullified your Torah” (Tehillim 119:126) .
This is astounding!
This is the verse used to justify Rabbi Yehuda Hanassi’s decision to commit the Oral Law to writing. In that case, there was a real danger that parts of the Torah would be lost. We can understand that in order to guarantee that the Torah itself survive intact, we might need to "nullify" parts of it. But to nullify the Torah to save a small segment of the population—poor mothers—some money seems a bit extreme. Surely another solution could be found; perhaps the community could have helped subsidize the price for those who could not afford such.
But Rabban Shimon ben Gamliel thought otherwise. Economic abuse cannot be tolerated, and if that means we must nullify the Torah, so be it.
The strategy worked. “The price of birds stood on that same day at one quarter of a silver dinar.”
 This is not the place for a full treatment of the Torah’s economic approach. For this, I highly recommend the books of Rabbi Dr. Aaron Levine, z”l, for further discussion. For our purposes, I will just state that while economic efficiency is a clear goal of Jewish teaching, economic activity can and must be conducted in a way that sanctifies the name of G-d by demonstrating that economic well-being and moral living go hand in hand. Given the importance of economic policy, coupled with man’s insatiable appetite for more, it is not at all surprising that there are more mitzvot in this sphere than any other in the Torah.
 With the rampant poverty of many in Eastern Europe, it was most common and most appropriate that many a community had only one or two sets of the arba minim that were shared by all.
 This is itself is a rather radical rabbinic interpretation of the verse. The pshat, plain meaning, of the verse is that when we see people violating the Torah then it is time we must act for the sake of G-d in order to uphold the Torah. Rabbinic tradition turns the verse on its head, interpreting it to mean that sometimes (very rarely) the way to act for the sake of G-d is by violating the Torah. As always, both the pshat and the derash are correct, each in its proper time.
 Rashi explains that what motivated Rabban Shimon ben Gamliel was his fear that with prices so high, many a woman would just not bring the required korbanot and yet would not refrain from eating sacrificial meat despite being in a state of impurity, a Torah violation that carries with it the punishment of karet. At the same time, there is a fear that some would actually pay the inflated price. While the former is a greater personal violation of Jewish law, the latter is a greater threat to the social fabric of society.