I disagree.
I suspect Detroit would make that trade without hesitation.
At 33, Chara was leading the Bruins to a cup, if you don't think Charra would have commanded much more than Larkin at that age, plus being relatively underpaid compared to his equivalent peers for the next 5 years, you follow a different NHL than I do.
Jagr at 33 was putting up 123 pts with the Rangers... Larkin??? Come on, get real.
You are seriously undervalueing what Crosby is, currently, on how rare/valuable that type of talent is... And very odd that you draw comparisons to players in their late 30's/early 40's. Not sure how old you are, but I can assure you that there is a massive physical difference between 33 & 38-39-40.
No reason to suspect a significant drop off in his play for at least 3-4 more years, then there are the intangible benefits that a GM like Yzerman does clearly value.