Customs anywhere in the world has their own rules in assesing the residual value of equipment you are trying to import. If its clearly second hand and you can show the age somewhere on the product (look for a manufacturing date on the stickers with the serial numbers) then they will use the residual value for estimating the applicable duty. If the invoice you show is only ~10% of list price and the goods are rather new you have very low odds in convincing the officer.

That said unless it is very bulky and flashy you unlikely to pass customs unhindered and no body will lift a finger not intercept you....