I think you need to dig deeper than that. Two organizations let him go because of his contract. It's not like he was making vet minimum and getting tossed around. He's making almost as much as Amir Johnson while impacting the game on the level of Solomon Alabi. Memphis moved him to get an expiring contract so that they could keep the band together. Houston is probably getting rid of him to free up even more space to make a move soon. They already were in the middle of a blockbuster that got vetoed by the league. They're dumping him for flexibility right now. The Raptors would only spend probably $1M to claim him.
I didthink about the money angle but to use your comparison he might just be another Alabi. In that case why bother. From some accounts Gray might be better and by getting Thabeet we'd also have to absorb the waived contract to free a roster spot. Again, not really knowing much about his recent play I am surprised how much he is considered a fall-off from his UConn days. I would leave this to the expert talent evaluators!