why did Indian peasants begin to agitate against the low prices of opium ?

(i) The British would procure opium at cheap rates. They would sell it at
a high price to the opium agents in calcutta, who then shipped it to
China.
(ii) This difference between the buying and selling price was the government,s
opium revenue.
(iii) The prices given to the peasants were so low that by the early 18th
century, angry peasants began agitating for higher prices and refused to
take advances.
(iv) some cultivators around Benaras stopped cultivating opium and started
producing sugarcane and potato instead. some cultivators sold off their
opium crop to travelling traders called pykars, who offered them higher prices.