Are the wife's family entitled to demand a "radwa" payment for her return, after her husband divorced her with a single pronouncement due to her leaving the house without his permission?

If the divorce is less than three pronouncements, it is revocable, and you have the right to take your wife back during her iddah (waiting period). For the revocation to be valid, it is not a condition for the wife to know or to consent. It is recommended to have witnesses for the revocation. The wife's family has no right to prevent her from returning or to stipulate money in exchange for her return.