Argument 1: Because it's not our money.
Argument 2: Because it's Gerrit F. Cole.
This should not be discounted as a throwaway argument. Gerrit Cole turned 29 years old three weeks ago, so technically 2020 will be Cole's Age 29 season, since he pitched the majority of 2019 at Age 28. If we look at B-Ref's Similarity Scores (scroll down), here are the ten pitchers most similar to Gerrit Cole through Age 27 (I guess B-Ref only updates these once a year):
1. Kevin Millwood
2. Cole Hamels
3. Dennis Leonard
4. Stephen Strasburg
5. Doug Drabek
6. Josh Beckett
7. Jered Weaver
8. David Price
9. Johnny Cueto
10. Ron Darling
There's not a ton to inspire confidence there. Hamels is...Hamels. Strasburg, sure. At some point I'll write a post on who the hell Dennis Leonard is, but after you've seen what has happened to David Price, do you want to commit $200m+ to that? Aha! But there are two stories here, because there are two phases of Gerrit Cole: Pre-Houston and With-Houston Gerrit Cole.
Pittsburgh Cole: 127 starts, 782.1IP, 749H/304ER, 734K:203BB, 67HR, 3.50 ERA / 1.22 WHIP, 112 ERA+, 15.4 fWAR
Houston Cole: 65 starts, 412.2IP, 285H/123ER, 602K:112BB, 48HR, 2.68 ERA / 0.96 WHIP, 164 ERA+, 13.4 fWAR.
That's right. Houston Gerrit Cole has been almost as valuable in just over half the starts as Pittsburgh Gerrit Cole. He's a different pitcher. The strikeouts have been discussed ad nauseum and, while the stikeouts are a perfectly valid part of the story, it doesn't tell all of it. With Houston, Cole went from an above average pitcher - certainly worthy of a 1-1 pick - to a Hall of Fame pitcher.
Consider that Cole has been worth 13.4 fWAR over the last two seasons. Here is the two-year peak in fWAR for members of Cole's "Similar Pitchers" list:
Dennis Leonard (1977-1978): 12.6
David Price (2014-2015): 12.3
Jered Weaver (2010-2011): 11.3
Josh Beckett (2007-2008): 10.0
Cole Hamels (2011-2012): 9.7
Kevin Millwood (1999-2000): 9.5
Johnny Cueto (2015-2016): 9.0
Doug Drabek (1992-1993): 8.9
Stephen Strasburg (2015-2016): 8.0
Ron Darling (1985-1986): 5.3
Two things: (1) Dennis Leonard? I retract my earlier slander. (2) Ron Darling benefited the most from being on a team that probably shouldn't have won a World Series. (Bonus): Stephen Strasburg? Maybe not worth the hype?
So, the point of this is saying Gerrit Cole is basically unbelievable. He has thrown 200+ IP in three straight seasons. His K/9 has increased from 8.7 in his last season in Pittsburgh to 12.4 in 2018 to 13.8 in 2019.
3. The Competitive Window of the American League:
Who is good right now? List them:
The Astros, the Yankees, the Twins, the A's, the Rays. Hey wow that's all the playoff teams from this year. Maybe you could slot Cleveland in here.
Next tier: Cleveland (?), Boston?
Further along in their rebuild: Toronto, Chicago, Arlington (?), Anaheim (?)
Gonna be a while: Baltimore, Kansas City, Seattle, Detroit
Point being that the Astros have a wide-open window to dominate the American League for the next few years, and extending Gerrit Cole throws that window open. The Yankees won't be hurt forever, I don't think. Oakland will literally run 25 Mormon missionaries out there for 162 games and still win 92 of them. So when the Astros have to take a step back once Verlander and Greinke retire and Correa does [waves hands] whatever he will do, and Brantley and Reddick move along, there's still Altuve, Bregman, Yordan, and...Gerrit Cole, and you probably have another few division titles, pennants, and who knows about World Series banners. Which leads to Point...
4. The Astros need a couple of years to develop their pitching prospects at lower levels.
With the Greinke trade, the Astros sent a couple of pitchers they were maybe counting on to contribute earlier to Arizona in Corbin Martin and J.B. Bukauskas. It doesn't matter that Martin won't pitch until late 2020 and Bukauskas has been an absolute roller-coaster over his entire career.
So who's left? Here's the last year the Astros have their current starting pitching staff:
On the other hand, the Astros have the following solid pitching prospects who just need some time: Jose Urquidy (not as much time needed, obviously), Forrest Whitley, Cristian Javier, Brett Conine, Jojanse Torres, Brett Daniels. Will they all pan out? Perhaps not, but having 2020-2021 with Verlander, Cole, Greinke, and McCullers will help the Astros keep the window open while they figure out who can stick.
It's worth it to me, because it's not my money that's being spent (and I distinctly remember the $26m Opening Day Payroll year), to extend Gerrit Cole. He's clearly the best pending free agent, the Astros have shown a willingness to extend their players (Altuve, Bregman, Verlander). Signing Cole to an extension means he doesn't go through what Keuchel or Kimbrel, or Machado or Harper went through last offseason. And extending Gerrit Cole means he doesn't go to any other team, those of whom are deemed threats to a dynasty the likes of which have not been seen since the 1990s Yankees.