700c rhynolite rims laced to surly hubs. Actually thats probably around $250. Don't know what you mean by inexpensive.
Or, just go to your local shop and ask what the least expensive 29er compatable rim is and lace it to any inexpensive cassette hub. You'll probably have to have it built, but if you get quality bike parts (QBP) to build it for you, it will be much less than the shop doing it.
But not all shops will deal with QBP.