The other issue with the larger lockers is finding one, you can be walking around for a bit to find an unused one especially if you don't know where they are located. Not something you want after a flight.

Last time I checked luggage it was 500yen a day for a large suitbag, top price you can pay is 800yen. They did ask me what terminal I was leaving from so like most left lugagge places I would assume you can drop off at one terminal and pick up at another. The question you have to ask yourself is how much hassle/risk do you want to save 5-10 dollars?