Keller catches too much flak from Jets fans. He's an above-average TE on a team that hasn't had an above-average TE in almost 30 years.
Gronk is averaging almost 9 mil/year. If Keller comes in at around 3 mil/year, it's a decent deal. You're not going to get more from the position than you get from Keller at less than that price unless you get lucky on a mid-round draft pick.