They are TOTALLY worth it.
I got my 2x4 tent from GYOsupplies (on ebay) for about $80 after shipping. My 5x5 tent from Best Choice Products, also found on Ebay, ran me about $160 after shipping.
They aren't necessarily the highest quality tents but they do the job for the price. My 2x4 is about 2 years old and is starting to degrade on me. Where the zipper meets the tent the constant zipping and unzipping has finally pulled a few threads loose. Needle and thread would be a solution... But I'm a man so I used duct tape. Works well enough.
The 5x5 I tore putting it together, I had to piss, and was working a little quicker than I probably should have been so I could put it all together. It is a small tear along the bottom corner and again... duct tape.
I swear by tents. They do require a decent amount of ventilation. My 400cfm inline fan in the 175cfm tent keeps my interior temperature about 3 degrees above my exterior temperature. My 180cfm blower keeps the 40cfm test about 6 degrees warmer than the intake. With an additional 4" axial fan as intake I can keep it within a degree or two. So I try to keep the bedroom around 71 to 73 degrees, I can use the fan controller on the 400cfm to control that deviation closer to the smaller tent's temperature.
I think a lot of people get into this with the idea of "oh, I just want to try it out." Then they do some research and realize just what is possible and things just snow ball.
I'm always devising schemes, browsing websites for product information and user reviews, and it just takes a while to soak in enough to understand the right system for you. Even now I look at the things I've bought, the decisions I made, and wish I could take it all back and start over and do it "right." Such is life. Though every day I think I can provide some guidance that is a little better tuned and understood. At least for a residential personal stash. I don't really know shit about commercial production of cannabis. I suppose it isn't all that different, just on a much larger scale at the cost of tens of thousands (if not hundreds of thousands) invested.
As reasonably young people (not yet 30) we have time to hone the indoor skills enough to one day grow outdoors at our own homes. I don't care what it takes, I'll have acres eventually, and I believe that all this is only going to help that process go as well as possible. Think of an above ground pool sized Ebb/Flow
Ahh, okay, I'm all baked and rambling now.