I am an engineer. We are not easily surprised . However I was pleased with the result of the estimate.
I usually gather boundary conditions, make assumptions if required and run the numbers. I might double check if the result does not match the initial gut feelings.
An additional knock out criterium for the alkalines was the disposal. On some weekends I run through up to 24 AA cells and maybe 1 9V battery for amateur radio equipment. It would literally hurt to haul that amount of cells to the store and throw it into their disposal box (as is the law here) on a weekly basis.