Components
- Transport: $1800
- Accommodation: $332
- Food: $275
- Communication: $60
- Entertainment: $60
- Goods: ???
- Shipping stuff home: $80
Total: $3007 plus whatever we spend on goods.
Transport
- Airfares estimated to be $1500 after all the fees and stuff
- JR pass should be $300
- Non-JR travel will cost extra, but probably not much, assume 3000 yen for time not covered by JR pass.
Call it $1800 for now.
Accommodation
- Nagoya: 1 night = 7000yen for 2 people (about 76AUD)
- Osaka: 1 night = $56 for 2 people
- Airbnb accommodation in Naka-Meguro will be about $200
Estimate $332
Food
Guessing $25 per day.
Estimate $275 after adding some fudge factor.
Communication
Phone rental and data SIM purchase?
Maybe $60 depending on how we do it.
Entertainment
Mostly arcade games and anything to kill time.
Estimate $60
Goods
- Otaku goods
- Cosplay goods
- Souvenirs and stuff that people requested
- Some may be repaid later
Impossible to estimate, assume hundreds of dollars 
Shipping stuff home
Call it $80 for now, may not be necessary at all.