I think his real value is extremely low also, but, within this particular wide receiver corp his potential value is very high.
I think a low 4th/5th round pick/player is what they might anticipate in return in a best case scenario. Most teams would likely offer less if there was interest at all. Playing the probabilities with what that might net, I don't see any reason to sell that low.
If he's playing 20 to 30 snaps per game, he's worth more than that to the team over the next season and a half.