I think it's hard to find a consistent price because some consider the Imperator IV to be a fabulous accordion, and thus worth a lot, whereas others realise that the Imperator IV is essentially just an Atlantic IV but with cassotto, and thus worth a bit more than an Atlantic IV but not a whole lot more, certainly less than a Morino IV. The Imperator has "Metalbau", meaning a metal case which can be pressed at once, in a completely industrial way, which costs much less than making a wooden case like the Morino has. Couple this with cleaper machine reeds (unless you have a "de luxe" version) as opposed to tipo-a-mano (hand finished) reeds on the Morino. Around here the going rate for an Atlantic IV is roughly 800 (between 600 and 1000 depending on the condition), a Pacific IV (not a popular model but essentially a Morino without cassotto) goes for around 1500 and a Morino IV for between 2000 and 2500. The Imperator sits between the Atlantic and Morino, so I rate it around what a Pacific IV goes for, which is around 1500.