Witten
393 catches
3,979 yards
22 touchdowns
80 starts
7.4 million per year, roughly $462,500 made per game started
Gronk
273 catches
4,222 yards
41 touchdowns
48 starts
9 million per year, roughly $937,500 per game started
Is Gronk a better player? Absolutely but he is also paid more. You said he is a better value and has outperformed Witten, I disagree wholeheartedly based on the numbers I posted above from the last 5 years. Yes, Gronk has more touchdowns, that is his role on his team--he is the redzone threat on a team without a big receiver. We have Dez for that and Dez rivals Gronk in touchdowns.
Witten is a reliable asset that is dependable on 3rd downs and he never misses a game. Gronk is making almost double what Witten is making per game started.
Gronk is the best tight end to ever play the game if he can actually stay on the field. I would rather have a steady player that plays every game than a great player that plays some games.