Add it to the pile:
2012:
https://pinside.com/pinball/forum/topic/pinball-price-bubble-think-it-cant-happen-think-again
2013:
https://pinside.com/pinball/forum/topic/pinball-price-bubble-will-pop
2014:
https://pinside.com/pinball/forum/topic/this-is-not-a-rebirth-of-pinball-its-a-bubble
2015:
https://pinside.com/pinball/forum/topic/we-all-want-the-ass-to-drop-out-of-pinball
2016:
https://pinside.com/pinball/forum/topic/when-will-the-stern-bubble-burst
2017:
https://pinside.com/pinball/forum/topic/are-we-in-a-pinball-bubble
2018:
https://pinside.com/pinball/forum/topic/why-i-feel-pinball-prices-are-going-to-plummet
2019:
https://pinside.com/pinball/forum/topic/will-pinball-prices-come-down-