Why does clindamycin cost so much more than benzoyl peroxide? When the effectiveness is about the same?

It is a prescriptive. BP is old technology and just drys skin clinda is an antibiotic that kills proprionobacterium which causes acne very different.
Both. Both of these medications have been shown to be effective for acne (and reducing the bacteria that plays a role in acne) and both are now available as generic medications so the price should be fairly reasonable (and similar). They do have different mechanisms of action and can be combined in a single product such as benzaclin, (clindamycin and benzoyl peroxide) duac, or acanya gel. Or, you can ask your dermatologist to prescribe them separately as Clindamycin topical solution and prescribe benzoyl peroxide 5% gel which might be a more affordable way to get the same medications. I hope that helps!