Here's a sampling of what GM's are paying major backcourt starters in the league (not on rookie deals):
Devin Harris 8.5M
Rajon Rondo: 11.5M
Joe Johnson: 22M
Deron Williams: 20M
Ben Gordon: 12.5M
Ramon Sessions: 5M
Derrick Rose: 18M
OJ Mayo: 4M
Ty Lawson: 12M
Andre Iguodala: 15M
Jose Calderon: 11M
Rodney Stuckey: 8.5M
Stephen Curry: 11M
Jeremy Lin: 8.5M
James Harden: 15.5M
George Hill: 8M
Chris Paul: 18M
Jamal Crawford: 5.5M
Steve Nash: 9.5M
Kobe Bryant: 28M
Mike Conley: 9M
Mario Chalmers: 4M
Dwyane Wade: 18M
Monte Ellis: 11M
JJ Redick: 6.5M
Eric Gordon: 14.5M
Raymond Felton: 3.5M
Russell Westrbook: 16M
Kevin Martin: 12M
Aaron Afflalo: 8M
Jameer Nelson: 8.5M
Jrue Holiday: 10M
Goran Dragic: 7.5M
Jared Dudley: 4.5M
Wesley Matthews: 7M
Marcus Thornton: 8M
Tony Parker: 12.5M
Manu Ginobli: 14M
Kyle Lowry: 6M
DeMarr Derozan: 9.5M
Mo Williams: 8.5M
At 8.5M (a price you said you would walk away at), Tyreke would be one of the lower paid starting backcourt guys in the league. This for a guy that even in a down year playing just above 30 minutes/game for one of the worst coaches and most dysfunctional teams, put up better numbers than most of that list. And he's 23 years old.
And with regards to the whole, he's gotten worse since his rookie season argument, here are his per 36 minute stats:
Rookie season: 19.5ppg, 5.1 rpg, 5.6 apg, 1.5 spg, .3 bpg, 2.9 tos (46%fg, 25% 3s, 75% ft)
Last season: 17.6ppg, 5.1 rpg, 4.1 apg, 1.6 spg, .5 bpg, 2.3 tos (48% fg, 34% 3s, 78% ft) This with the ball in his hands less, getting yanked around in positions and with no real team development at all.