Cost of alk drink will vary according to use of ingredients.
But to compare with cal mag, you would need to take quite afew other things, and they are not available in as easily absorbable forms for any price, as far as I know.
The unique thing abt the alk drink is the chemical synergy that makes all ingredients more assimilatable, not just the calcium and magnesium!
Comparing cal mag with the alk drink is like comparing the wright bros biplane with a spaceship!!!! Just not in the same class!!!!