Stevenson and Anderson were not one hit wonders. Both of them had a few good years here. Not just one. Those are just examples of the Jazz system making players better. Matthews won't be nearly as good somewhere else unless it was someone like the Spurs.
Matthews better defense and better outside shot is worth the money. Miles is way too inconsistent on defense and offense. He has mental lapses and coasts. Matthews is also a better passer and slasher. He runs hard even in a half court set. Miles does not.
Stevenson had 1, Anderson had several, but bottom line is they overall had average or below careers. That may happen to Wes too, and it is a risk when considering 7 mil a year offer for 5 years, when we already have starters in place.