Is it illegal for employees to earn the difference through internal purchase?

Legal analysis: illegal. Employees violate the relevant regulations of the employer and infringe on consumers' right to know. If the amount of the difference earned is relatively large, the act constitutes a crime of job embezzlement and is sentenced to fixed-term imprisonment of not more than five years or criminal detention; If the amount is huge, he shall be sentenced to fixed-term imprisonment of not less than five years and may also have his property confiscated.

Legal basis: Article 271 of the Criminal Law of People's Republic of China (PRC). Personnel of companies, enterprises or other units who, by taking advantage of their positions, illegally take the property of their own units for themselves, if the amount is relatively large, shall be sentenced to fixed-term imprisonment of not more than five years or criminal detention; If the amount is huge, he shall be sentenced to fixed-term imprisonment of not less than five years and may also have his property confiscated. Personnel engaged in public service in state-owned companies, enterprises or other state-owned units and personnel appointed by state-owned companies, enterprises or other state-owned units to engage in public service in non-state-owned companies, enterprises or other units shall be convicted and punished in accordance with the provisions of Articles 382 and 383 of this Law.