Ask myself the same question at least once every season.
$20 should cover a bag of something cheap and decent like Roots Organic. A bale of Promix HP on that “Brazilian River” is only $50 shipped to your door.
$100 is probably minimum to get a light worth having. It’ll get you a 400w HID, 200w of T5, or 100w of LEDs, all arguably putting out about the same amount of useable light.
Nutrients are kinda all over the place and people start getting all up in their feelings about the best one. You can get a kilo of mega crop for like $10 right now with their two promos.
The General Organics box is like $30 for a decent beginner line.
Even some of the absolute top of the line nutrient companies have a “no-frills” option of the necessities for $50-60. That’s a can of worms you’ll have to open yourself though.
Puts you between 150-200 dollars assuming you already have a perfect spot to grow them. Timers, yo-yos, and power strips add up real quick.
Damn, I didn’t even count operating costs...
Assuming 12/12 from seed for a minimum of ten weeks — 12h*70d = 840 hours of light @$.10-$.20 per KwH
*400w HID = 336KwH, $33.60-$73.20
*200w T5 = 168KwH, $16.80-$33.60
*100w LED = 84KwH, $8.40-$16.80