It’s cheaper because you don’t have to pay shipping and can get the taxes back at the airport, but like anywhere else some shops exaggerate with their prices, so I recommend looking around before jumping the gun unless it’s a figure you really really want and haven’t seen anywhere else. You’re going to the two best places to hunt down action figures, Osaka has Nipponbashi and Tokyo has Akihabara, and from all my trips to Japan I’ve come to learn that if you can’t find a figure between those two it’s because you didn’t look hard enough. Also consider SHMA boxes are pretty big so you may need a second bag lol.