from what I believe the prices started going up when JJP came on the scene so Stern started to raise there prices a few hundred almost each new game release, then second hand sterns started to go up to stay $1-2k under a NIB and then overseas container pins followed suit but there is some crazy priced container pin prices now for 20-25 year old games. I could be wrong but pretty sure the AUD has remained similar to the Euro so the price shouldn't have gone up so much for the overseas purchase but more so the Aussie sellers raising prices to stay within reach of second hand sterns.
So you think Stern started the price rises that then flowed through to the classic DMD's? Interesting. Strangeways will probably have a handle on this given he was bringing classic DMDs in through this period. Maybe for another thread as getting off topic, sorry Swinks!
This thread is going a bit off topic, but the quick answer is that although both NIB and Container pins have increased in prices, the price increase of container pins is 100% due to greedy dealers listing $9500 "Fully done up" Twilight Zones that have been very poorly shopped. Once one dealer sees a TZ at $9500, they automatically adjust the price to that figure and now ALL dealers "think" TZ is a pinball they sell for $9500 all day long. Which is not true of course, but once the overseas suppliers check Aussie eBay - they see the games they are supplying are advertised at massive profits, so overnight, they increased their supplier price. Which in turn drives up the selling cost which introduces cost cutting in Australia.
The bubble for NIB Sterns will burst a lot sooner than the 25 year old pinball's bubble will..
But in 25 years time, collectors will be asking for Stern titles to be restored as they are the games they identify with as well.