Is the sale valid if there is a mistake in the goods received or in their agreed-upon price?

Since the error occurred on the part of the questioner, and he accepted the other type in the first example, and the price in the second example, the sale is valid in both cases, due to the fulfillment of the condition of mutual consent from both parties. This is in accordance with the Almighty's saying: "O you who have believed, do not consume one another's wealth unjustly but only [in lawful] trade by mutual consent," and the Prophet's (peace be upon him) saying: "Indeed, sale is by mutual consent."

The validity of the sale in the first example follows the Maliki school of thought, which validates a contract in which there was an error regarding the specific item being contracted upon, and grants the party who was subject to the error the option [to revoke the contract], drawing an analogy with a defective item.

As for the second example, its validity is evident based on the buyer's acceptance of the seller's error. This is supported by what is stated in "Umdat al-Fiqh" by Ibn Qudamah and its commentary by Al-Baha' al-Maqdisi, where one party is compelled to accept if the other party is content with what was claimed.