Having monopolised the league trophy as well as the All-Ireland for most of Jim Gavin's reign, the Dubs are back in a Division 1 decider for the first time since 2018.
In between, they have hoovered up four more All-Ireland championships, 'shared' a league title with Kerry in 2021 (their prospective championship meeting was to double as a league decider but it never happened), took a surprise spin in Division 2 and then returned.
Under Dessie Farrell, we had grown accustomed to their league form being slack. Shockingly, they were relegated in 2022, a notion which would have been borderline surreal a year later.
Their ultimately successful run through Division 2 was largely swagger-free, with Farrell admitting after a forgettable win over Limerick that they "looked like a Division 2 team today." Not that any of that counted for much later in the year.
The start of this year's league appeared a continuation of that trend, although Dublin have taken wing after two opening losses, embarking on a run of form reminiscent of their salad days under Gavin.
"Things are starting to click, there was no silver bullet there," Costello tells RTÉ Sport, when asked to account for the uptick in form.
"The first game against Monaghan was a really poor display from ourselves. Again, maybe a little bit of ring rust or whatever you want to put it down to.
"Second game, we actually thought our performance wasn't too bad. Mayo were very good on the night and they fully deserved their win. But we didn't think it was the worst performance in the world.
"Just the last couple of games, offensively, things have clicked and we've been a lot more clinical in front of goal.
"Things seemed to marry the last couple of games, which is great. But at the same time, it is the 26th of March and it's early days yet."
The fears among the rest of the country about perpetual Dublin dominance had abated somewhat in the early 2020s as the age profile of the team finally ticked upwards and the emerging generation struggled to make an impact.
While the famous '93s - Fenton, Kilkenny et al - remain the backbone of the team and will likely remain so come championship, some of the younger brigade are beginning to come of age.
Worryingly for the rest, Costello suggests that they're adjusting to Dublin's very honed and well-established patterns of play in possession.
"There's a couple of guys who've been on the panel for the last few years," says Costello. "And it takes time.
"There's a bedrock there of systems of play and set-ups, that's nearly second nature to some of us older guys because we're used to it for years upon years.
"But it's a lot of information for someone to come in and retain. You need time.
"The Allianz League is great for breeding lads into the system and getting used to playing a certain style.
"Theo Clancy made his league debut, Greg McEneaney stepped up, Killian McGinnis. Guys who are early 20s, even teenagers.
"We're pushing on, us older guys. It's important to breed those guys in."
The pick of Dublin's performances was naturally the 10-point win over Kerry in Round 4, in which they racked up 2-11 by half-time with barely a wide kicked.
Tyrone, meanwhile, got to experience what it was like to be Leinster championship canon fodder in Croke Park last weekend, as Dublin ran in five goals by the 50th minute.
As impressive was their five-point away win over an otherwise flawless Derry in Celtic Park in Round 5, though Costello, like every other Dublin player since, has stressed that the hosts rested a couple of big players, notably Conor Glass.
"They're (Derry) table-toppers for a reason. The Derry team that we played up there was a weakened team too.
"There were a couple of key guys missing. We're expecting a different beast on Sunday.
"They're in great form. They're great to watch as well. They bring an intensity to their defence but also to their attack as well. There's some serious and silky footballers there."
In a strange coincidence, the final is a repeat of last year's Division 2 decider, which Dublin won with a curious score tally of 4-06. Despite finishing runners-up in the standings - which would be the end of it if some reformers had their way - they are favourites heading into the final.
Not that any outside narratives impinge on Costello. The Whitehall Colmcilles player, who said this week he's big cricket man ('Royal Challengers Bengaluru' man for life, apparently), claims not to pay much attention to Gaelic Games coverage outside of playing the sport.
"Personally, I don't read too much into GAA. I try look at other sports when I'm not playing football.
"Because GAA, although it's a hobby, there's a lot of time put into it. Sometimes it's nice to detach from it and watch other sports in a more relaxed kind of fashion.
"So, I'm kind of out of the loop. A lot of my friends are into other sports, which is kind of a relief. There's not much chat about GAA to be honest."
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