The single most common comparison mistake is comparing two supplements as if their servings were the same unit. They almost never are. Before you can say one product is a better value than another, you have to convert both onto a shared yardstick, and that yardstick is the amount of the ingredient you actually care about per day.
Start by writing down the serving size for each product and the amount of the key ingredient per serving. Say Product A delivers five hundred milligrams per serving with a serving of one capsule. Product B delivers two hundred fifty milligrams per serving with a serving of two capsules. On the shelf they look like rivals. On paper, a single serving of A carries twice what a single serving of B does.
Now pick a target amount and express everything in terms of it. If you wanted to compare them at the same milligram level, you would need two capsules of B to match one capsule of A. That changes how fast each bottle empties and therefore changes the true cost per day. Comparison is meaningless until both products are speaking in the same milligrams-per-day.
Once the amounts are normalized, recompute servings per container in those normalized terms. A bottle with one hundred twenty capsules of B is not one hundred twenty servings if you need two capsules to match your target. It is sixty. Suddenly the bottle that looked like it would last twice as long lasts the same time, and the value gap you imagined disappears.
Watch for products that quietly shift the serving size to make a number look bigger. A larger amount per serving is not generosity if the serving is also larger. The amount per capsule, or per gram of powder, is the figure that resists this manipulation, because it does not let the label redefine the unit underneath you.
When you finish, you should have a small table in your head or on paper: amount per day, cost per day, days per bottle. That table is the only fair side-by-side. Everything before normalization is the marketing department's preferred comparison, and everything after it is yours. What that normalized amount should be for you is a question for a qualified healthcare professional, not for the label.