I've also noticed during my trips that electronics are not always cheaper even during enyasu times.
I did ask at the Tsukumo Ex to verify and they did confirm (at least in their store) that the yen price will fluctuate with the exchange rate so more times than not it's fairly equivalent to the dollar price and waiting till I get home from my vacation to just order online or buy locally saves on the hassle of the tax free procedures and carrying it around/back with me to the US.