You can look around but trust me, those are the best prices you'll get. I know because I was thinking of ordering some for my gym or possibly importing weights myself. So I keep track of local sporting goods and prices.
You won't believe what most local places charge for a set of Olympic plates and a bar: NT$60,000 is the norm. Benches usually go for around NT$30,000. Compared to that, $15,000 for a set of plates and $9000 for a decent bench is a steal.
If I were you though, I'd seriously consider this power rack:
It's only NT$8,700 and you get a pull down station. That plus a separate bench would be a better deal IMO than the bench above.
Your other option is what you've already found: the youth weight sets with the screw-on collars. Yeah, they suck and you can't put up much weight but they're a bargain compared to Olympic sets here. Good luck.