legal analysis: this is not illegal, it belongs to the middleman to earn the difference, and it does not violate the relevant provisions of the law. It is not illegal to buy and sell new or second-hand goods as long as it complies with the relevant regulations of the platform.

Legal basis: Article 225 of the Criminal Law of the People's Republic of China violates state regulations and commits one of the following illegal business operations, thus disrupting market order. If the circumstances are serious, he shall be sentenced to fixed-term imprisonment of not more than five years or criminal detention, and shall also, or shall only, be fined not less than one time but not more than five times the illegal income; If the circumstances are especially serious, he shall be sentenced to fixed-term imprisonment of not less than five years, and shall also be fined not less than one time but not more than five times the illegal income or confiscated of his property: (1) dealing in franchise, monopoly goods or other goods whose trading is restricted as stipulated by laws and administrative regulations without permission; (2) buying and selling import and export licenses, import and export certificates of origin and business licenses or approval documents as stipulated by other laws and administrative regulations; (3) illegally engaging in securities, futures and insurance business without the approval of the relevant competent department of the state, or illegally engaging in fund payment and settlement business; (four) other illegal business activities that seriously disrupt the market order.