Why is OKX ripping us off?

Does this make sense? On OKX the current BTC price is 88.7k (Singapore currency) but when I preview my purchase it’s 90.0k. 1.5% higher! I’ve never seen these sort of fees written on their fees page. This page actually says “no fee” which I find highly misleading. I like the interface and also tried trading with USDT, however that’s also got hidden charges with the SGD to USDT conversion too. I bought a large amount and despite BTC going up 4% I’ll be breaking even if I sell now… I previously came from Moomoo which is a nightmare to use, however their fees were tiny in comparison. Anyone else analyse the fees they are paying? I want to start sinking large amounts over the next 3 years and don’t want to get ripped off.