Before the success of the American Revolution, the colonists were under the domain of Great Britain. Not too surprisingly, in an era in which communication between the two countries could take months, and in view of the distance between Great Britain and America, decisions that were made in Great Britain would not necessarily be well and thoroughly considered, especially since the colonists had no representation, in regards to being able to express in Parliament what was most appropriate for those colonists. Further to the point, decisions that might make sense, financially or on paper, could find that their implementation of, would ensure unexpected consequences.
In point of fact, the Tea Act, by Great Britain, would on the surface, appear to be beneficial to the consumers of tea in America, for the British East India Company Tea would now, with the new law and being the sole authorized provider of, have their imported tea priced below the market price of such tea currently being distributed in America. However, the error so made by British governance was that by deliberately and unexpectedly undercutting colonial merchants of tea, who themselves had acquired a great deal of their tea through illegal shipments and through non-authorized means -- this would effectively negate the value of their inventory, and therefore harm their businesses, irreparably.
So then, in knowledge that the sheer amount of tea at the Boston harbor, would materially damage domestic vendors and merchants, should such be unloaded onto the docks of Boston, the concerned and well placed influential denizens of Boston, made a conscious decision to preclude such unloading of tea, and further, under the disguise of being American Indians, forcefully took such tea and dumped it into the ocean, in order to destroy it.
So that, in effect, the colonists united to protect their domestic businesses at the expense of the country that was its governing hand. In other words, the colonists would not countenance their domestic industries being materially damaged, so that their mother country, could thereby benefit at the expense of those colonists, for they recognized that if the colonists were seen as something for Great Britain to tax and to milk for the benefit of Great Britain, directly -- while the colonists suffered to be exploited by them, then the colonists did not have effective liberty, but instead were subservient to a country, on an entirely different continent.
When we subsequently fast forward to today's America, recognize that when products that are imported to America with cheap labor, often with suspect environment and working conditions within those foreign nations, of which, these products have no tariffs or other restrictions placed upon them, so that these foreign companies are able to successfully compete and quite often dominate against domestically manufactured American products, then domestic manufacturers are not going to be able to hold a candle to those imported goods. This, in effect, enriches those foreign nations and the international companies that aid or are conjoined with them, at the expense of the domestic working citizens of this nation, who are now unemployed, or employed at a lower paying job, of which, today's America, gladly unloads and thereby sells this new Boston Tea.