Not that he's not reselling them, but paying a 9% tax for every single item you posses beyond $500 in value every time you cross the border is just absurd. Remind me to never take my laptop, phone, or a decent camera anywhere near Singapore.
All that aside, I thought the idea of customs and import duties was versus new items, not things that can be picked-up at a second-hand store or pawn shop. If he provided itemized receipts, would they even believe him if the prices weren't high-enough? ... or were "too old"?