Thanks again Magnus,
We're down to a small gap under discussion. You are at "great deal" and I'm at "good deal". But I hope we haven't scared off the original poster with all this talk. The simple message is "buy". :D
And I'm one of the people who bought an old K at a really low price (in Feb 2014). An 18" old stamp (IVa) which weighs in at 1290g. My total cost? $160 (US dollars). No shipping because I drove across town and picked it up.
I also suspect that the extremely good deals which some people get (and then post about online) is one of the things which really gets people excited about these and keeps the adrenaline flowing. The thrill of the hunt for that fantastic deal...because prices are so variable and not all sellers are "in the know". ;)