Consider this a little primer with conditions, probiotic names and prices.
Probiotics come in two main forms: food and dietary supplements. There are so many different brands and formulations and quality control is not well regulated. The effectiveness is specific to the disease and the dose taken.
1. Diarrhea after taking antibiotics (or to protect your GI tract when you take an antibiotic)-
DanActive - $5
Align - $50
Bio-K+ - $17-27