I agree that hotel prices are always pretty high in Singapore.
The old faithful for the budget conscious used to be the Phoenix Hotel on Somerset and Orchard. But I believe that closed for refurbishment in July.
It too had varied reviews, mostly due to its tired state. But if the sheets are clean and the AC works, what more can you want in Singapore - you'll only be there for sleeping, and don't worry about the Hotel Food, there's so much to eat elsewhere.
Try directly on some of the big brand websites - sometimes you can hit it lucky and get a bargain price.
I recommend
thiswebsite for ease of searching for hotels in any budget in Singapore.