Maybe if you brew some super tea using high quality humic acid, guanos, enzymes, b vitamins, chitin, etc the cost could become higher than buying a premade compost tea. You still can't buy a bottle that contains the same kind amount of bacteria as a freshly brewed tea.
I personally don't think you need to go expensive at all. You can use nothing but manure and get a very active and rich tea. A lot of people like to introduce over ripe fruits, rice wash, aquarium water, protein meals (such as milk, alfalfa, soy, bean, rice, oatmeal, etc), any manure/guano, molasses, mushroom compost, outdoor made compost(ie. from various yard and kitchen waste, worm castings, kelp, expired fruit juices, dolomite lime, bone meal, blood meal, human piss, etc.
All of those aren't really expensive other than say worm castings, guanos.. it gets expensive when you add enzymes, b vitamins, chitin , salicylic acid, plant hormones, "lab grade" bacterial/fungal inoculants.
A lot of this stuff anyone can afford to use. You could use manure, rice wash, a handful of soil (for it's diversity of bacteria and fungi), and some overripe fruit and you've got everything you need for a rich compost tea.
The process usually takes 24-36(up to 72hours if temps are low)hours to make a tea, from what I've read closer to 24hours is best to keep diversity in the beneficals.