The currently invitation-only Dropbox Basic Extra plan here in Australia is advertised at $2.99 a month. However, when you click through on the invitation to purchase it becomes $3.29 a month, due to the addition of GST (Australian version of VAT or Sales Tax) at 10%.
Just flagging that it's illegal in Australia to advertise prices exclusive of GST.
I get why it's happening and that it's not intentional, but reckon it's something you'll probably want to remedy.
The normal dropbox plans available at https://www.dropbox.com/plans are fine, they all include GST in the advertised price.