The official term for this is COPS (cost per service) and it helps you greatly in making smart economic decisions. I calculated this for many household products about a decade ago and came to the conclusion that for many products it’s barely worth worrying about the cost while for others there’s hidden cost that should really warrant closer inspection. For instance dish soap has such low COPS that it almost doesn’t matter which brand you buy. Electric gadgets like fridges, washing machines or printers definitely warrant deliberation though because in the long run energy, refill, maintenance and repair costs will approach if not outstrip the initial purchase cost.