Usually, Apex & I are pretty close to the same page. In this case, I disagree.
After watching rollbacks, for a while now, it seems that an old truck just about doubles in price, with a slidebed attached. Don't forget, that rollbacks, and wreckers see a lot of idle and idle bump time, so the engine hours could be very high, versus the mileage.
Looks to me like the cheap trucks, are old cargo rigs. The bonus to that is, you can pull the box and use it for storage, and still have a fairly inexpensive truck, to pull a 5er.