The Pact of the Tome warlock is able to learn ritual spells of any kind and record them in their book of spells. Wizards also can learn new spells and record them in their spell book– but the PHB explicitly requires them to pay a cost in gold and time to record the spells (i.e. 50 GP per spell level in addition to 2 hrs per spell spell level of time).
Do warlocks with Pact of the Tome have this same requirement? My guess is no, but I can’t find a definitive answer.