I think many hobbies can fall into this, depending on how far down the rabbit hole you go.

For example I got way into building scale model airplanes a few years ago. Now, you can buy a small 1/72nd scale airplane in a kit WITH paints and brushes for like $20. Good fun.

But then you look into different tools, and become interested in the very excellent results produced by an airbrush...Cheap chinese Airbrush is $20 but now you need an airbrush compressor. Okay thats another $80. Wow some of these airbrushes are really nice...Okay lets get a Made in USA Badger Airbrush. Boom $75. Wow ze Germans make a great airbrush too...I can use the cheap chinese one for clear coat and primers...And the Badger airbrush for bulk work...And the German Harder & Steenbeck airbrush for detail work...Wow Iowata looks nice too, highly recommended and most of the chinese knockoffs are clones of these...Well I might as well get one of those too so I can compare it to the others. Next thing you know you are hundreds of dollars deep into airbrushing stuff and an ever expanding array of paints, primers, glues, tweezers, files etc.

Speaker building is another one. Originally it seems like a cool project, work with your hands and buy kits that when built can compete with the high dollar boutique speakers. Blow those high end Klipsch speakers out of the water for 1/4th the cost. Then a few kits later you are eyeballing kits that cost $400 per speaker and again an ever expanding array of tools to do the building with.