《民法典》第580条第1款但书第2项规定，当债务人承担的非金钱债务的履行费用过高时，可免除其实际履行义务。该规定在调整合同双方的利益关系及保障市场秩序稳定方面具有重要意义，然而，由于其内容表述较为模糊和宽泛、缺乏具体的司法解释，导致在司法实践中难以准确把握适用标准，文章将分析该规定在司法适用中存在的问题，并提出完善的建议。
文章首先对最高人民法院公报案例及其他相关司法案例进行了分析，揭示了当前“履行费用过高”规则的适用现状及存在的问题。这些问题包括论证不充分、履行费用的构成不明确、判断“过高”的参照对象和标准不一致等。接着，文章探讨了履行费用的理论内涵和正当性基础，以揭示该规则背后的价值取向，并从适用前提、可归责性、是否以债务人违约为前提、适用合同关系类型方面区分了履行费用过高与情势变更的不同。最后，对履行费用过高规则的适用标准进行了探析，履行费用的范围应包括金钱成本、机会成本和时间成本，应当排除执行成本和精神损害等非经济因素；在判断履行费用是否“过高”时，应以债权人的履行利益作为比较的基准，当两者都能完全以金钱衡量时，可借鉴30%的量化标准；而当两者无法单纯以金钱量化时，“过高”的判定需要法官进行个案衡量，综合考量债务人的可归责性、债务人自身的履约意愿与能力、合同具体内容，以及替代交易的难易程度等，并在上述量化标准上进行微调，以实现个案的平衡。

Article 580, paragraph 1, item 2 of the "Civil Code" stipulates that when the cost of fulfilling a non-monetary obligation assumed by the debtor is excessively high, the actual performance obligation may be exempted. This provision holds significant importance in adjusting the interests of the contracting parties and ensuring the stability of the market order, and should have considerable applicability. However, due to its vague and broad content and the lack of specific judicial interpretations to supplement it, it is difficult to accurately grasp the applicable standards in judicial practice.
The article begins by analyzing typical cases from the Supreme People's Court Bulletin and other relevant judicial cases, revealing the current status of the application of the rule and the existing problems. These issues include insufficient argumentation, unclear composition of performance costs, and inconsistency in the object of reference and criteria for judging "excessive". On this basis, the article explores the theoretical connotation and justification of performance costs to reveal the value orientation behind this rule, and differentiates the differences between the rule and changed circumstances in terms of applicable prerequisites, accountability, whether the debtor's breach of contract is a prerequisite, and the types of contractual relationships.
Finally, the article analyzes the applicable standards for the rule of excessively high performance costs. The scope of performance costs should include monetary costs, opportunity costs, and time costs, and should exclude non-economic factors such as execution costs and mental damages. In assessing whether the costs incurred for performance are "unduly high", it is essential to consider the creditor's performance interest as the reference point for evaluation. When both can be fully measured in monetary terms, a quantified standard of 30% can be referenced. When it is not feasible to quantify the two aspects solely in monetary terms, the determination of "excessiveness" requires the judge to assess each case individually, taking into account a variety of factors, including but not limited to the debtor's culpability, the content of the contract, the debtor's own intention and ability to perform, and the difficulty of alternative transactions. Adjustments should be made to the aforementioned quantifiable criteria to achieve a balance in each specific case.