Are probiotics a scam treatment?

No. They are definitely good medicine in some conditions. Probiotic meds are even used in the hospital for some causes of diarrhea.
No.... and yes. . There are studies showing the benefits of probiotics for certain narrow conditions and other studies show no benefit. So there are some good uses. Problem is advertisers make billions off promises that probiotics will cure everything. Not true .
Probiotics--worth $. "pro"-biotics put good organisms into your gut (unlike "anti"-biotics which kill bacteria) & include: lactobacillus, acidophilus, bifidobacter, sachromyces boulardes, to name a few. Most are available over-the-counter, and may provide (in some patients): less gas, regulated bowels, prevent infections (like C.diff), improve digestion, decrease inflammation. Check prices & desired benefits of each.