We stayed in the Wolcott:
http://www.wolcott.com
Which was easy walking distance from the centre of Manhattan and was clean and comfortable but was nothing special (better than a hostel though)!
Try booking it through expedia (try combined with flights and without) for the cheapest deal, it should work out cheaper than quoted on their site. A continental breakfast is included (basically muffins and coffee)
I can't give you an exact figure of how much we paid but we stayed in it for 6 nights and paid under �500 for it plus our flights from UK