I very much doubt someone will be prepared to pay another $8 or so on a $10 item just to have something the next day.

You'd really be surprised.

A number of my listings have Express post as an optiopn and buyers regulary take advantage of it.

The other day one of my buyers paid the extra $8.50 for express posting a $4.95 free post item.

If buyers need an item urgently for a special occasion they are prepared to pay whatever it costs to receive it before the weekend.