Used price for steel tubeless big truck wheels, is usually around $50 each, depending what it is and where you are, that sounds fair to me, I would not pay much more unless they came with inspectable tires, then around about $100 each.
For new prices you will need to go to your local big truck tire shop and ask them to check the price on that part number.
Those wheels may not be extremely easy to find used, but I would say not difficult. I have seen a number of trucks with that size bolt pattern 22.5 wheels.

Grigg


1951 GMC 250 in the Project Journals
1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-