Pet fee
What a hotel charges for the dog, per night or per stay, on top of the room. It is the least advertised number in hospitality: ask for it in writing before booking, and whether it includes anything (bed, bowls).
Two hotels that both admit dogs can differ by a lot once this appears. Ask three things in writing before booking: how much it is, whether it applies per night or per stay, and what it includes, because some properties count a bed and bowls in it and others charge a cleaning supplement on top. The property's own answer is the one that counts.