I thought the only steel wheels for our trucks were the ones used by the PPVs/SSVs and aren't they 17's?
Not sure what your definition of "inexpensive" is but I got some factory wheels from a non-LT Suburban for $140, but they were 16's. Keep checking CL, the 6 bolt pattern is quite common. If you can find someone who bought a new truck and just wants to get rid of his old wheels you can often find a good deal. Make sure you search "chevy" "GMC" "avalanche" "Silverado" "Sierra" etc as well as Tahoe and Yukon.