The $1000 exemption is a 'de minimis' exemption because it's not worth customs inspecting the goods and filling out the paperwork at the border. It now only applies to low volume senders from overseas.
Large senders like AliExpress, Amazon, and eBay (>NZ$1M/year to NZ IIRC) are required to collect GST on all sales with no exceptions, because the cost to them of building GST into their ordering systems is deemed minimal compared to the total amount of GST collected. I believe YouShop falls under this.
Duty is additional to GST and refers to specific taxes on certain types of goods (i.e. tariffs) - common examples are alcohol and tobacco. I haven't looked at whether brake levers (vehicle parts?) would attract a duty.

