I'm going to be boring and say it's not worth it most of the time. I used to do this when I was a teenager and couldn't get hold of the components. Nowadays I don't bother, unless it's something expensive or exotic.
Ditto. But given the ongoing shortage, I'm not surprised that this activity is getting popular again.
Its also the weirdo millennial crowd that uses magical thinking to will things in to being recyclable that are not.
Germane to a few posts above, my interest in building a small parts inventory of relatively known components from teardowns of things related. Its not like I tore down a microwave board for parts to use for fixing a meter.
More than the money, its the annoyance of constantly needing to pay shipping for a single tiny part and the waiting period when you have nailed a problem and want to just see it fixed. For this reason, I started to break down boards from stuff that was not savable. Whether it yields any useful pieces is to be seen.
Your best bet is to bulk order a load of commonly used parts.
Start with:
E12 resistors from 10R to 1M, with extra 1k, 10k and 100k because they're very common.
E3 capacitors from 100pF to 1000µF, with extra 100nF and 10µF because you'll find those everywhere!
BJTs: BC338 and BC328, BC139, BD140
MOSFETs: 2N7000 and IRL3705
Voltage regulators: LM317, LM78L05
Op-amps LM358, TL072, NE5532, OP07
Logic ICs, not needed so much now, but still handy: 74HCT14 Schmitt trigger inverter, handy from shifting 3V to 5V and building oscillators, HEF4504 handy to shift 5V to 12V.
LEDs: various colours.
Microcontrollers: choose a range with a cheap and widely available programmer and preferably GCC support, so you're not tied to it. Many people here like AVR for that reason, although I've not used them myself. I have a stock of old PICs, but they're not supported by GCC and have quirks, so I wouldn't recommend them to a beginner.
Miscellaneous: switches, relays, small speakers, buzzers etc.
Power supplies and test equipment.
Consumables such as solid core, insulated wire, flexible cable, heat shrink tubing, strip or perf board etc.