Yes, it's law here that you're only liable for tax on the amount you actually pay.
There was time (a couple of years ago?) when Sideshow was neglecting to put the discounted price on the customs declaration. So you'd get the VAT and Duty charged on the full retail value, then have to fight FedEx for a refund.
Sideshow claimed they were required to put the full retail value down, but they eventually changed their tune.
Not as good as the time they were sending items from Hong Kong and declaring the value in HK$ so you only paid a little bit of tax if any. R5-D4 was so cheap that he was actually tax free. Sideshow unfortunately discovered and rectified that error, and I chose to go back to using FedEx from the US.