At the risk of sounding heartless, between $2.00 and $10.00, assuming you can find someone to buy it (Some exceptions are mentioned below).
Lest you protest, I have to remind you of a few things about collectables:
Sad but true. But think of this as a great opportunity to start your very own Polaroid camera collection! These cameras are neat to play with and collect, and are inexpensive. Plus, if you collect pack film cameras, you can still use them to take pictures since film is still available for them.
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. There are many Polaroid cameras listed on Ebay that will never sell because the starting bid is too high.
There are a few models which are worth more than a few dollars. These include the 110 series (Pathfinder) of roll film cameras (which can fetch $40 or more), the 180 and 195 ($200+), and SX-70 foldable cameras ($20+). The dollar values here are intended to be just a guide.