You are describing it like it's some sort of natural process rather then the result of a deliberate British policy to ban the spreading of industrial technology and introduce price distortions to strangle Indian industry. The logical place to make textile mills in the idealized market was India, that was where there was a large textile industry and where cotton was grown. In order to prevent that you need to ban the sale of industrial machines to the Indians and then collect your taxes in agricultural products but not manufactured ones.
And this wasn't some insignificant or short lived policy. The American revolution can be traced to the backlash against British efforts to kill early american industries in printing, iron smelting, even hats. The Opium wars aren't called the Textiles wars because the British wanted the Indians selling an agricultural product which wouldn't compete with British industry.
Yes, but you are ignoring the fact that economic nationalism was still strong in the 19th Century. The USA and Canada did the same things to the western provinces, and in Canada's case, the Maritimes.
The Maritimes had a pretty prosperous economy until the National Policy screwed things up. It never really recovered, since it lacked the resources the West had to recover from that.
India was just that on a much larger and powerful level, in many ways.
In any case, in general, a pretty good rule of thumb is that colonies can be divided into 4:
Trading Outposts/Plantation/Island Colonies (Hong Kong, West Indies, Oceania): Highly profitable. Everyone likes Sugar, Coffee, and everyone wants to trade something with China- unless you're Chinese. They
can be hard to hold on to, and defend, though.
General Asian: Pretty high development potential due to high levels of resources, population, and basic infrastructure. Can have high cost to take over- but almost always profitable to some extent once you do for all involved entities.
Settler Colonies (Americas, Australiasia): Not always profitable (sometimes unprofitable, like French Quebec), but economic development potential high. Plus, lots of feedback effects that eventually go back into the treasury from private companies.
African Colonies: Good luck making money from these. No infrastructure (minus N. Africa- but
the Ottoman Empire wasn't all that great making railways), leading to few extractable resources, and thus potential cash.
Unless you're the Belgian Congo, S. Africa, or Egypt. These go into the "General Asian" Category.
Fur Colonies: Profitable, with little needed infrastructure. But Fur eventually gets out of fashion... and that land could be used for something else, a lot more useful. Like farms.
