fry the fat out of To obtain money by high-pressure tactics or extortion; to milk, put the squeeze on. Just as the frying process removes excess fat, so does extortion or high-pressure fund-raising tactics remove the “fat” or excess wealth from the affluent. This now little-used U.S. slang expression dates from the late 19th century.

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Note added at 18 hrs (2012-11-01 13:45:49 GMT)
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"ya se había acostumbrado a escamar peces más gordos" would fit your context better. (Peces gordos being "fat cats")