Common

 In my experience these pins are readily available through retailers, Internet or eBay and  are mass produced.  For this reason, they are reasonably inexpensive and should cost up to $10

Limited

Slightly rarer pins either due to them being produced in limited numbers, or due to their age and therefore more difficult to track  down.  Expect to pay a little bit more for them, between $10 and $50, as you will be vying against other collectors.

Rare

Very difficult to get a hold of due to the very limited number produced.  Press Pins fall into this category, with the older ones being extremely scarce.  This is reflected in the price, which can reach hundreds, if not thousands, of Dollars.