As others have said, getting a luxury hotel in Zurich at a decent price is pretty much impossible, and Switzerland in general is pretty expensive.
Not sure whether you´re really looking for a true 5*, over-the-top experience (think top 10 hotels in the country) or whether a solid 4.5*+ hotel would be sufficient (e.g. Montreux Palace in Switzerland). I often find those hotels (think Fairmont, top Intercontinental/Hyatt hotels) to provide much better value for the money I spend, the marginal benefit of spending twice or triple at some point is minimal.