Forget about the money. If we have 'fielding independent pitching', then maybe we need money independent pitching. Control what you can control (evaluation) as the contract is already in place. There's no judgment applied to chicken and beer or anything else.
First, there are the raw numbers, tenth year in the majors, sub 4 ERA and good winning percentage (poor way to judge pitching). 2010 was Buchholz's best year with a spike in 2013 curtailed by injury...which is always his story. His adjusted ERA+ is just over 100, meaning he's been just slightly above average for his career. Discounting this season, Buchholz had 44 wins in the past five seasons...just under NINE per year (yeah, I just said don't judge wins). Including this season, however embryonic, Wade Miley has 45 wins and pitched at least 190 innings four times (straw man argument!). Steven Wright has a better chance to be an innings eater than Clay, who has never thrown 190 innings (second straw man).
As far as the more advanced statistics, Buchholz (in the past five full seasons) has a WAR (wins above replacement) of 8.2 or 1.6 per year.
The "eyeball test" says that Clay Buchholz has better than average stuff...a solid major league fastball, and better than average changeup and curveball. Sometimes, he seems reluctant to work the inside of the plate to right-handers, but I digress. But the numbers speak volumes. Whatever the cause, health (esophagitis issues ostensibly from medication), injury, lack of toughness, or unfavorable astrology, he's an average, non-durable pitcher who has had a couple of terrific seasons. Expecting much more from him, especially slotted as your number two, is unrealistic.