I have been reading multiple articles related to free agency this year, and it comes down to this.
There aren't very many FA WR that are very good. Watkins, despite his production, is regularly listed anywhere from #1 to #3 on list of FA WR's teams are likely to target. And when supply is low and demand is high, prices skyrocket.
Someone like the Bears is going to step up and offer him solid WR1 money. Sammy is going to make bank.
For the team, I think the best approach is to sign a 1 year prove-it deal and then prepare to really pay in 2019. But there is no reason in the world Sammy would take that with what teas are likely to offer him.
As I see it right now, the only way we retain Sammy is to either match the market in terms of contract or franchise him. And even if we match the market price,I could still see him going elsewhere where he will be the primary target rather than one among many.
Hope I'm wrong, but that is how I see it right now.