The problem with Tavon isn't that he lacks value.
The problem is the price tag.
The Rams gave up too much (trade up, No. 8 pick) and are paying too much (2nd highest player on the team) for a guy who is a role/gimmick/decoy player.
It doesn't matter for this year - he's going to be paid, so they should get as much out of him as possible - but next year they may have to consider whether there's a guy in the 4th/5th round of the draft who can perform his role (speed guy for jet sweeps, fakes, occasional runs from backfield, etc.) at a much lower price tag.