Yeah, for a 2x4 you need about 400 watts. Not that bad. It's the guys who go to 5x5 (1000w) and larger that really start to spend the coin.
But really, a 2x4 with a 400w light can get you 8 oz dry bud every 90-110 days (perfect grow). If you can do the veg on the side, you can drop that to every 60-75 days. I guess if you want 1.5 pounds dry weight in those timeframes, you gotta kick up the coin flow.
But what I was getting at is the cost to stay current. Dump your hid and get cobs. Dump your cobs and get qb. Dump your qb and get?
Oh, and you will need c02 once you get everything dialed in. Controllers, generators, and now you need a/c and dehumidifiers plus all the digital controllers to keep everything in balance.
But wait, now you need to upgrade your electrical service because 2 x 20 amp circuits isn't enough.
And you won't want to stay in dirt at that point. So it's hydro or aero. More equipment, and controllers, and an RO system, and a whole line of more expensive snap's.
And of course, you need supersized filters to scrub the air.
And security. All the punks in your neighborhood are gonna think you have pounds of pot and lots of cash on hand. All of your hard work are belong to them.
It's a never ending escalation.
Meh, I'm not interested in an arms race. I'm just going to enjoy the zen and have some fun. If my current light dies, I'll build a diy with whatever is riding high. If I don't get 2g/w, or even 1 g/w, I'm not going to tear everything down and build it back up.
But if you have the resources. Go for it. I like the vicarious thrills.