I sent off my parcel of Christmas presents this morning. It's going Surface which cost me 4000 yen. If I had waited until later and sent it Airmail I would have had to pay 10150 yen so it was worth getting it off early.
The cut-off dates are coming up for Surface but you still have time to shop and mail your parcels Economy Airmail (SAL). For Surface mail I think the US cut-off is November 1st, for New Zealand it is mid-November.
Have a look at the Japan Post website, it's all in English and quite user-friendly.