Im just starting a grow using URB. I applied urb three plants in veg and the effect was positive and plainly observable in 2 days. Ive also used soil balance pro, sea green, recharge, mammoth and tanio spectrum PSB. These products have big followings and committed users because they are effective, far more concentrated than brewed tea and easy to measure and apply. The specific strains used in these products trigger specifc quality enhancing reactions in plants. In my personal experience SBP applied one time to a house plant resulted in the production of oil coating many leaves, overnight. Using a drench of sea green it was obvious that the microbio changed the atmosphere in my flower room by increasing CO2 through microbio respiration.
There is plenty of science validating the effectiveness of concentrated microbio products on soil health and crop production and quality. A little research would demonstrate that the trend in agonomy for hemp, cannabis flowers and highest quality food crop production is biological innoculation of soil.
These products are no joke, no one is trying to trick you or steal your dough.