I'm active in the trade market, that's how I've always experienced it. One of the owners in Piazza likes to frontload FA demands as signing bonus and then have minimum salary contracts, and then trade them for some reason. So it's always a sweet deal because he is eating the bonus while the other teams are acquiring the lower salary
I also learned a lesson the hard way in Reynolds... At the end of the most recent season I had about $10M in unused salary at the end of S39 so I went into my S40 free agents to see if I could extend the S40 guys and have the signing bonus go onto my S39 payroll. Nope. Lost $7M on the S40 ledger which hurts, but now I know