Will a mistake in value of the subject of the contract allow a contract to be rescinded?

No, even if both parties were mistaken.

No, if only one party was mistaken.

Yes, if both parties were mistaken.

Yes, but only if the contract is for less than $250.

In a contract where there was a bilateral mistake of fact:

one party misunderstood a word or term in the contract.

both parties misunderstood a word or term in the contract.

one party misunderstood the value of the subject of the contract.

both parties misunderstood the value of the subject of the contract.

Would one party's mistaken belief about the law governing a contract be enough to rescind the contract?

Yes, even if the other party had no knowledge about the mistake.

No, because a mistake about the law is not factual.

Yes, because it is a mistake about the law.

No, because it is unilateral and concerns the law.