Unlike so many of you, my main non-audio/non-headphone hobby is quite inexpensive: vintage calculators. I bought two at an estate sale yesterday, a TI SR-10, so vintage that it is heavy, chunky, has tiny, red LED numbers, and the label on the bottom side calls it an "electronic slide rule calculator'; and a TI-35, much more modern, using an LCD display. Half a buck for both. I also got [dirt cheap] an Olympus XA-2 with flash, a minor classic. All three units worked when I got them home and installed batteries. I have, I suppose, a few dozen old calculators. It all began in the winter of 1969/70 when I discovered a room at college which contained nothing but one table, some chairs, and Wang calculators with nixie tube displays. I just loved them.
Photography [big Olympus fan, I regularly take better photos than my ex who has a Nikon 8008] is a hobby too, and cycling. My mountain bike is retired, and when I ride, it is on a vintage [that word again] Peugeot road racing machine which I have re-done as a hybrid. I have to deflate the tire to take the rear wheel out of the frame, the tires are so fat.
I also collect stone balls. Yes, I have about a dozen balls...
Laz