Another classic factor in psak that causes poskim to rely on positions they wouldn’t normally rely on is hefsed – monetary loss. Shiur and sources (including many summaries from Encyclopedia Talmudit) are available: here.
That the Torah cares about the economic stability of the Jewish people is clear. There are two formulations of this that are explicitly connected by the Yerushalmi (and many Rishonim and Achronim). Specifically, the notion of HaTorah Chasah al Mamonam shel Yisrael, the Torah had pity on the money of the Jews, and the dispensation found throughout Shas in cases of hefsed merubeh, great economic loss.
The former concept explicitly appears in Shas to explain why certain mitzvoth are patterned the way they are. For example, the Gemara explains that while the Kohen Gadol uses a golden shovel for the ketoret on Yom Kippur, during the rest of the year he uses a silver one, so as not to incur extra expenses for the Jewish people. The exact parameters of this principle are unclear. Continue reading God is Concerned about the Jews’ Money (Halachic Methodology 11, Shaat HaDechak 3)