How much money did you spend in Japan?

I’m heading to Japan in two months for 42 days. I’m backpacking and wanting to keep costs quite low where possible. I’ve already spent $2000 on accommodation, $900 on flight, and am planning to spend roughly $1200 on food ($30 AUD per day). In terms of buying things there, I can’t buy heaps considering I will only have a backpack and not much spare weight to bring heaps back. How much will I be expected to spend besides these things? Obviously another big one will be transport, but aside from that, is there anything else I am forgetting? Does under $6000 AUD seem achievable or am I dreaming?

by Separate_Treacle_633