I have just 'recycled' a couple of hundred linear feet of 2 x 4 from a ceiling I took down. It got reused in part of the replacement ceiling. I had to remove about 7 lbs of drywall screws (CT-12) and buy a metal detecting wand before I worked on it. I visually checked the surfaces - somewhat discoloured - but the wand told me what I needed to know. I 'detected' a piece of metal in a number of pieces and I made a choice as to whether to dump the wood or chop around it. Once I had done that I carefully rechecked every piece slowly - and found one missed broken screw. Then I felt confident about running the HL850 over the surfaces and cleaning them up.
Now, take into account the cost of my time (free, but has a value), the special handling, the dust bags, potential for needing new blades, etc., it was probably just about worth it over buying new (given the inexpensive quality of the wood to begin with). But I also did it to see what was involved in the process. Also the wood was full of stains that would not come out. Other sources of wood may not have some of the same issues. I know someone who built furniture from old school desks made of oak. He had enough to be able to select the less marred pieces for the outside and also did a good line in veneering them when needed.
If it had been recovering hardwood then it might be somewhat more economic. However I did learn: 'Scan twice, not once'.
My 'scanner' is a Lumber Wizard III. It worked well enough to detect the small screws in the table underneath the wood I was scanning and the small pieces of screw ends. Out of curiosity I ran it over my new wood as well and found several staples from the labels.
SteveD