Speaking after the race, Kostecki joked that Erebus CEO Barry Ryan should give him extra brownie points for making the podium alongside Reynolds: "I'm sure Barry will give me a big bar tab because of that".
The Boost Mobile-backed driver added he is happy with how his first season was going, having already formed a strong bond with fellow rookie Will Brown.
"I absolutely love Erebus and we have really enjoyed ourselves this year," the 23-year-old said.
WATCH: ELATED KOSTECKI'S FUNNY TAKE
"Now we've had a taste of champagne, I think we need to push harder throughout the rest of the year and get some more of it.
"Learning from each other is the only way to go about both being rookies.
"He's going to do some things better than I can and I'll do somethings better than he can, so if we can combine the two together it helps the greater good."
Although still developing a relationship with engineer George Commins, Kostecki expressed his elation to bring home the trophy for him so early in the piece.
"George and I get along really well," Kostecki said.
"I made him cry after the race, so I have one up on him at the moment."
As for if he would consider the empty seat at the Red Bull Ampol Racing for the 2022 season, with Jamie Whincup retiring, he gave a definite answer: "No, I've got both hands down.
"Someone ese can have a crack."
Kostecki now sits 10th in the championship, five places ahead of Brown.