My preliminary apologies for this long post. If you're inclined to skip it, I urge readers to check out the 2 links at the end.
There are a lot of valid opinions in these "value trend" threads. In the end, the same arguments tend to surface, e.g. the perennial nostalgia "cargument," the "dying out collector" contention, the "old technology isn't as much fun" theory, the "irrelevant Americana motif" notion. I suggest that while there's a kernel of truth to these stereotypical observations, no single point has predicted the ebb and flow of pinball pricing these past 35 years. As evidence, I offer the fact that prewar game prices have steadily risen during that period, particularly notable over the last 15 years and even more so in the last 3 years. Since these prewar games were on location in the mid-1930s, the persons who actually played any of those games on location would be over 100 years old today. Those centenarians are not buying these games, needless to say. Thus, the "dying out collector" contention fails to explain why prewar prices have actually steadily risen. Prewar enthusiasts, like me, never played these prewar games on location.
I am 61 years-old. We are men and woman who love coin-op in general. We likely have trade stimulators, soda machines, stamp machines, and/or EM arcades punctuating our pinball line-ups. We appreciate the magnificent ingenuity and inventiveness of the prewar game designers. We have learned that very little in today's modern games is new. The 1930s prewar designers included, flippers, ramps, kick-out holes, trap holes, multiplier scoring, multiball modes, mystery specials, light shows, ball advance features, you name it. Once an enthusiast discovers this fact, he/she tends to broaden his/her pinball horizons and may want to acquire a prewar game or two. I recommend that prewar neophytes google "Rockola World's Series," "Jigsaw" and "Army Navy" as a primer to the marvel that is the prewar era.
Another factor which affects price is the expanding "age of information." Early in the hobby, EM parts were difficult to find. Many enthusiasts would shy away from EMs, fearful about the ability to repair a game and/or secure a required part. Collectors relied on trade magazines, limited pinball and Americana-type events, the Google group: rec.gamespinball and the yahoo prewar pinball group. Pinside was in its nascent stage. Often, a collector would have to fabricate parts. Within the last 5 years, in particular, access to parts has burgeoned. For example, the EM Facebook group began in late 2014. Today, 6 years later, it boasts a membership of 7,200 enthusiasts. Members post videos of malfunctioning games and obtain excellent trouble-shooting advice within minutes. Pinside repair threads offer similar help. Also, the advent of 3D printing has greatly expanded the ability to create previously unobtainable unique parts.
As others here have stated, prewar and EM games, when played regularly, are far more reliable than solid state games. With regard to woodrails, I find many of the 1954 Gottliebs to offer as much fun or more fun than any other pinball from any era. That's because those games were designed for the player's enjoyment, as opposed to operator profit, which had a greater design influence in the years to follow. The year 1954 is notable: Gottlieb Grand Slam, Niagara, Daisy May (and 1952 Queen of Hearts, the favorite of famed designer Wayne Neyens) and many others are examples of pinball's pinnacle, in terms of player-oriented objectives. Each offers multiple paths to a special. As I recall, Grand Slam offer 7 routes to same. Moreover, the Roy Parker art on these games is no less than spectacular.
My line-up has been populated by 1930s games and every decade thereafter, up through JJP's WOZECLE and Stern's The Beatles. I love the classic Bally-Williams titles (e.g. TZ, AFM, CFTBL) and the classic Sterns (e.g. Stars, Medusa, Fathom, Quicksilver). Gradually, I have concentrated mostly on EMs, with 70s pinball and arcade games having the greatest appeal to me. I suspect that enthusiasts who dismiss "older games" as slow, boring or otherwise inferior have probably relied on poorly-shopped games, played at shows, or else many have never immersed themselves in the best representative titles of the era, in well-tuned condition.
I'm an advisor on a documentary film entitled "Arcade Dreams" (formerly entitled Welcome to Arcadia), to be released in theaters and/or perhaps on Netflix 2021. In that film, we seek to explore the history of pinball and arcade machines. The vibe is sort of PBS meets MTV. I think that many Pinsiders will enjoy it. Here's the 3 minute trailer:
https://arcadedocumentary.com/
Below is a 12 minute mini-documentary segment (filmed in my basement---to resemble an arcade) in which I discuss the history of EM arcades, including classics like Sega's Gun Fight, and how those games were the progenitors of modern home video games. Here's the link:
https://vimeo.com/373213017/6b7c121826
The director and crew previously made the documentary "Viva Amiga," a retro love letter to fans and creators of the Commodore Amiga, a machine which changed the way people viewed computers. They have a plethora of fantastic footage for Arcade Dreams, enough for a series. Arcade Dreams is an overdue tribute to all that we love about pinball and arcades, and its nod to history really helps us understand the games we play and enjoy so much today.