I'm Singaporean... and in Singapore right now.
You're looking at the most expensive stretch in Singapore. It's along Orchard road, our main up market shopping area in the city.
On the other hand, Singapore room rates aren't really that expensive. The Ritz Carlton is 300+ SGD a night, and most of the other 5 star hotels are around that range. So I'm not sure where you got 400+ USD from. Unless that's like the price for a suite?
If indeed that is the price you face, perhaps you can consider checking out "Orchard Parade Hotel" or "Goodwood Park Hotel"
Goodwood is right next to Hyatt, while Orchard Parade is about 5 min walk away. Alternatively the Meritus Mandarin at Orchard Rd is also just across the road. They should all be around the 300 SGD range for a room.
Or how about letting us know your budget?