There are some wonderful places in NZ but no luxury hotels, a few luxury lodges and B&Bs (these run in the USD 1000+ per night range). Otherwise not much in between (hard to spend over USD 100 per night). If you are looking at the top end, Huka lodge is it (one of the best in the world).
http://www.hukalodge.co.nz/
Otherwise, see
http://www.friars.co.nz/