I think the miss in this logic is the classic HF fallacy: GMs aren't exclusively about managing the future. GMs are paid to make money, and to do it for as long as possible. You're not looking at "late 1st to go over the top", you're looking at "how much is what I'm giving up going to do for me/cost" versus "how much more revenue am I generating this year by having Kreider in the fold?"
Conservatively, let's call a playoff home game an average of $150 a seat, and 18000 attendees. It's playoffs; assume a sellout. On ticket sales alone, that's 2.7 million dollars per game in additional revenue. That doesn't count beer, food, merch, etc. Extrapolate - A Stanley Cup Finals run that features 12-16 home games is probably worth around $50 million in total revenue. Adding a round to your playoff run is like adding some 7 million, minimum, to your coffers.
Obviously, that number goes up as the rounds increase, and obviously there are revenue sharing components here, but your calculus is probably more like "Does what I'm getting increase the chances of securing an additional round? More than one?"
A decade ago, I read where average FB sales was about $16 a game per patron. Got to be $25 or more now. 18K x $25 x 30% for net is about $135,000 per game. Parking has to average $30 for those who park, but many come by public transit, so say $20 X 18,000 at about 75% profit and it's another $270,000. Who knows on merchandise.
So, a total playoff game might bring in over $3M. 2 playoff games nets you a star player in salary. I think most teams budget based on making at least one round of the PO.
Not to mention, I bet the Blues have upped both STH and gate sales by 15-20% this year. While regular season games vary and will be less, maybe $2M per night, or $82Mil in game revenues a year, adding $12-$16 Million the next year is a nice boost.
That said, if you ask any GM, its all about winning, baby! Especially on deadline trades. Seems to me the appetite for these trades, and thus, prices in general for rentals, has gone down the last few years. How many teams have acquired a bunch of big name players and won? A better approach is to acquire someone who fits your bill perfectly and not much else. And preferably well ahead of the TDL, to help build chemistry.