Are we clear now? Are you convinced I'm not advocating making your own electric power generation stations?
I think this was a terminology misunderstanding - I don't see it as "the answer". "The answer" in my book is specific for each particular situation and your guideline is important to take into account for each such situation. I'm splitting hair now, but only to illustrate the source of misunderstanding.
To advance the state of the art it would help if you created a list of cases where "build" produced unexpected advantage and a list of cases where it backfired. At least it would work better for me to calibrate properly.
EDIT: It just occured to me that you answer to my answer is what curried function is to a function result. Throw in lazy evaluation and the line gets blurry. :-)
actually, scratch that, it's even better when time and money are tight
in my case, i bought baking, washing soda and lye for my hygiene. 5kg each, each kg lasts for a year. extremely cheap (like $1/kg). only one time transaction.
i no longer go to soap, toothpaste, detergent and drano section when i go to grocery. suppose that takes 5 mins for searching, picking up, queueing and paying for each hygiene run while in grocery, it easily adds up to 52*5 = 260 mins time not wasted per year.