“不惜工本”可以翻译为“spare no expense (in doing sth.)” 或者 “go all out in terms of cost/expenditure”。
“spare no expense (in doing sth.)” 强调在某件事情上不吝啬花费，愿意投入大量资金，例如：They spared no expense in renovating the old mansion.（他们在翻新那座旧宅邸时不惜工本 。）
“go all out in terms of cost/expenditure” 侧重于表达在成本、开支方面全力以赴，不计较花费多少，比如：The company went all out in terms of cost to ensure the project's success.（为了确保项目成功，公司在成本方面不惜工本 。 ）