Regehr is different, he's a UFA after the season. Ownership doesn't care about trading away draft picks, they care primarily about two things; revenue and on-ice performance. Regehr costs very little, due to being a UFA, and the trade doesn't subtract anything from the on-ice performance, only enhances it. Easy sell.
$3.5 million IS a decent price for a 1st/2nd line winger. Jokinen is that only in stretches, hence why he was dealt away for a 7th round pick. If he was a guaranteed top two line winger, he'd have fetched a lot more than that at the deadline.
Telling your owner, whose money it is you are using, that you're picking up a guy with $3.5 million left on his deal and that in all likelhood you will be buying him out after 10 games plus the playoffs isn't an easy sell. Put it another way. $3.5 million for 10 games is, prorated, equal to paying one player $28.7 million a season. That's nuts. And you can't convince anyone that Jokinen is the difference in making $3.5 million in extra revenue. Jeff Carter, sure, he has that elite level skill set to be a top performer, Jokinen doesn't have that same pedigree and disappears for stretches, including this year. And historically speaking, Jokien hasn't had great starts in new locales. With Tampa Bay he had two goals and 14 points in 20 games while with Carolina he had one goal and 11 points in 25 games. Combining those two, he had three goals and 25 points in 45 games after moving to a new team prior to this trade deadline. That's NOT 1st/2nd line winger material.
And all of this doesn't factor in that if we don't buy out Jokinen we are essentially right at the salary cap for next year and have no room for improvements.