“and who enriches himself by keeping goods taken as a pledge.” The literal Hebrew is difficult due to the culture and idiomatic use of the language. The Hebrew text is more literally, “who makes himself heavy with heavy debts [or, the weight of pledges].
The idea is that the wealthy powerbroker makes loans and takes collateral (the NAB reads, “collateral,” while the CJB, HCSB and NRSV read, “goods taken in pledge”), but then ends up keeping the goods he has collected, making himself rich. Because the collateral he has taken are material things and have weight, the reading of the Hebrew text, “makes himself heavy with…” is very accurate. Some versions nuance the text and read “extortion” (cp. NET; NIV; NLT), but while this is easy to understand in English, it is not exactly accurate. Although extortion may well be involved in some cases, what the powerbroker is doing is closer to simple dishonest business practices. Making loans then figuring out how to keep the collateral, perhaps by charging excessive interest and claiming the loan was never really repaid.