A buddy of mine got a bottle of it for around $50. I don't think you need it if you're using anything stronger than a 600w lamp, definitely don't need it at all outdoors. 600w and under, I would follow Mary Jane Monkey's suggestion to save product. I use Miracle Grow Bloom Booster 15-30-15 at 2.5ml a Gal from the first sign of hairs showing until they get too dense to dry off quickly to avoid mold, under 1000w lamp.

I've read that Liquid Light is for growers using weaker lights in the 250-600w range, nevertheless, if it's possible to spend $50 for light in a bottle, and reduce 1000w to 600 or less to save electricity.... I guess it depends on the results and your electricity rate. Somehow I think you will save money by reducing electric use and spending the difference on Liquid Light. That's of course, if you can tolerate foliar feeding, whether you're indoor or outdoors, and what mold problems you might encounter. I mix Neem Oil at 5ml a quart plus the Bloom Booster, and it works good. No mold, no mites, no burns. Plants stay green and healthy until molasses knocks out the nitrogen.