Imagine you are buying a car.

By comparing similar makes and models you get an idea of what is a high price and what is more middle of the road.

Also, if you have an idea of what you are buying, and what it compares to, you will have some awareness of what is rare and exceptional about the item you are looking at and why it might command a higher price.

So have a look around, find things that compare to the piece you are looking at and see if you can find anything like it.

You can always ask a dealer about what makes an item worth its price.

A good dealer will have prices based on current market values and should be able to justify the asking price.