Is there a legal text that approves the marriage of a daughter in exchange for the marriage of a son, especially given the difference in time periods and costs between the marriages of sons and daughters? And how are the different marriage costs calculated over time, with changing prices and purchasing power, when dividing the inheritance?

The share of each heir from the deceased father's estate must be determined. The guardian of the orphans (the father's appointed guardian, the judge, or the mother according to some scholars) must safeguard their money, spend on them, and invest it. When an orphan reaches maturity and sound judgment, their money is handed over to them. It is not permissible to marry off any of the orphans using the general fund, and there is no such thing in Islamic law as marriage in exchange for marriage, because that constitutes an aggression against the orphan's money. If the money includes forbidden usurious gains, these must be removed.