Risk proposes raising credit lines by $2,000 for 100,000 good customers. We expect each account to carry about $400 more in balance, at a 20% APR and a 5% cost of funds. But this group has about a 2% annual default rate, and people who default usually max out their lines first. Is this line increase worth doing?

风险团队提议给10万个优质客户每人提额2000美元，预计每户平均多出400美元余额，APR 20%，资金成本5%。但这批人一年的违约率约2%，而且违约的人通常会先把额度刷满。这次提额值得做吗？