Glad you feel that way. All year long we've heard about how Sammy got a lot of attention from defensive backs, opening things up for the other receivers in a way that most receivers wouldn't have. Which is why many feel that the Rams' offense wouldn't have been near as potent without him, especially early in the season when Goff was still learning a new system and needed help, and needed a confidence boost. But you don't believe any of that.
Of course, given how high his salary ended up being bid, apparently a lot of pros DO think he was very good for the Rams in 2017.
Incidentally, since the Rams will almost certainly get a third for him, saying the Rams should have traded no higher than a third is basically saying he was worth loaning a pick for a year. That would be a great system.
Thing is, for $690k the Rams got 8 touchdowns, which strikes me as a bargain.