It can be very difficult to answer the above question.  Thankfully, there are experts and reference resources which can help.  But, in the end, the truest answer is:  It's worth what someone will pay for it.  With that being said, for those of you who may be new to the hobby, we've assembled a checklist which we hope will help give you a general idea as to the value of a particular bottle.  Remember that, even though a bottle may not be considered valuable to us, it doesn't mean that there aren't others who may consider it of some value (an Ebay audience for example).  And, of course, what is beautiful to you, or has sentimental value, is priceless.