The short answer is, "Probably less than you think."
Polaroid made literally millions of instant cameras and there are a lot of them sitting in attics waiting to be discovered. After Polaroid discontinued production of all film, followed by Fuji in 2016, the utility value of roll and pack film cameras has fallen. Since the Impossible Project (later Polaroid Originals, then just Polaroid) resurrected SX-70 and 600 film, cameras that take this type of film have gone up in value, but since they also produce new cameras which cost around $100, that has put a damper on camera values.
Probably one of the better indicators of value is to monitor Ebay closing bids on your target camera. For instance, if you are looking for a model 450, search for "Polaroid 450" and watch the items and take note of their closing bids. Bear in mind that a seller may ask whatever he chooses for a camera, but it's the closing bid that reflects the value. Many Polaroid cameras listed on Ebay will never sell because the starting bid or buy it now price is too high. To get a picture on closing bids, follow the auction and check the bids after it has ended. The closing bid, if any, will be indicated on the item page. If the camera you're interested doesn't have any bidders, you can assume this is not a sought after camera.
Here's my take on camera values:
You will probably find many people trying to list low end Polaroid cameras (especially with a bellows) for $100 or more. They are trying to sell it for antique value, but are unaware that these are not cameras that collectors generally look for. And since film is not available (unless converted to another film format), they are only useful in a collection.