The Diamondbacks don't have a long history of extending players early, which isn't surprising, given the short history of the team, the more recent trend of signing young players early, and that the Diamondbacks didn't have a ton of high profile new players until after 2004.
An early extension comes with the excitement that one of your favorite players might have more security, and it excites the news cycle. But it also comes with the dread and perhaps eventual dislike if the player doesn't live up to what is often a modest raise.
It's easy to see why teams like early extensions, as it create certainty in future expenses. Players largely like it because it also takes away from the risk that they'll get injured before any payday. Early extensions can also help alleviate the general fact that young players are grossly underpaid, whilst older players are grossly overpaid to make up for this. Although these extensions rarely pay the young, producing player their full value as they're earning it, the extension can help bridge the gap. See the recent Mike Trout and Angels controversy for an example of a team choosing to not extend early and instead take advantage of the fact that they don't have to offer him anything more yet.
The following players are all ones developed (or largely developed) by the Diamondbacks, and received a larger payday before they reached the end of their rookie contract. It's not a long list, and although the aforementioned risk certainly carried with all of them, I think the high-profile nature of the names shows that the Diamondbacks have been pretty good about signing early.
- Byung Hyun Kim - Before his 2003 pay raise, Kim was better than gold for the Diamondbacks. In 3 1/2 season he never had an ERA+ lower than 100, and racked up 7.6 bWAR as our funky reliever. In 2002 he saved 36 games and was named an All-Star. It wasn't more of the same after his big bump from $762,500 to $3,250,000, being shipped off to Boston midseason after struggling as a starter, and then being kicked around the league for the rest of the decade. If there's a sunny side for Arizona out of this is that we didn't have to pay the higher contract for very long.
- Brandon Webb - His pre-2006 contract extension fairly modest at 4 years and $19.5MM, but if there's a guy who earned it in spades before and after, it was Webb. 14.4 WAR in 3 seasons before, 19.1 in 3 season after, along with 1 Cy Young Award and 3 All-Star Appearance. The end to his career may have had a little bitterness and tragedy to it, but no one can ever accuse Webb of not earning his money. Hopefully it's set him up to great lifetime of deep sea fishing.
- Chris Young - Signed after his very good 2007 rookie year, in which the D-backs also stormed the playoffs, this was a more extreme example of the "sign early" trend. The prior two guys had a few years to show their stuff and had more traditional signings. Young was locked up early, so didn't have a big record to point towards. His 2007 season almost had a 30-30 in home runs and steals, but overall he only earned .7 WAR. His 2008 campaign was a disaster, but the big money didn't start rolling in until 2009. Overall he earned 14 WAR on his $28MM contract.
- Mark Reynolds - Signed right before the 2010 season, Reynold's contract was also escalating towards $7.5MM a year for $14.5MM overall. Before the contract he earned 5.1 WAR, but he only lasted 1 season and .4 WAR before being shipped off to Baltimore. Another case where the Diamondbacks didn't have to assume the largest part of the contract, but also a case where the faith wasn't rewarded.
- Justin Upton - Also signed before the 2010 season, Upton's 6 year, $50MM deal was pretty splashy. It was also considered a steal after his 2009 All-Star year, and people expected big things. He earned 5.1 WAR in 2 1/2 seasons before, and 10 WAR in 3 seasons afterwards, with another All-Star appearance and leading the D-backs to the 2011 playoffs. Now he's with the Braves.
- Paul Goldschmidt - Reported at 5 years and $32MM, it's probably not going to break the bank. Up to this point in 1 1/2 seasons, Goldschmidt has earned 3.6 WAR. Here's hoping he's more like Webb or Upton, and not traded away instantly like Reynolds or Kim.
So there you have it, the very short history of the Diamondbacks Early Extensions. I might have missed one or two, and I have no doubt someone will remind me in the comments. There's not a lot of history to go on here, and approximately $6MM a year isn't so bad for a guy with Goldschmidt's power. Hopefully he'll continue to mash.