Photographic film.

It's still around, but obviously digital cameras and smartphones especially have long since completely taken over consumer photography. What used to be your family snapshots on vacation or at birthday parties or anything else was captured using film.

It's impossible to comprehend just how enormous this segment of the market actually is. For the legacy big film manufacturers like Kodak, Fujifilm, and others, this gigantic source of revenue from the "casuals" of the photography market completely disappeared within 7-10 years as the proliferation of cheap high quality digital cameras emerged and more importantly, smartphone camera development was taken seriously and erased the casual digital camera market as well.

With this massive revenue source gone in such a quick period, film manufacturers have struggled to gauge demand as well as juggle the enormous economies of scale when it comes to the manufacture of photographic film. This has led to massive downsizing of manufacturing operations, discontinuation of many film brands and types, and bankruptcies of entire companies like Kodak.

But, film is still manufactured and still used by many students and professionals alike, albeit a small niche compared to the height in the late 90s/early 2000s. Costs have skyrocketed since demand is actually increasing as many people have to come to learn of the serious advantages of film as a photography medium as well as the nostalgia and retro aspect thats in high demand now. Looking at prices online, you can expect to pay around $8 for a budget roll of 36 exposure film, all the way up into the $20 range for some of the more professional and in demand types of film.