There's probably an argument to be made that the Jays shouldn't touch Bruce, but if the Reds or Angels send some wallet over then that really mitigates the cost. It could have ended up being a negligible bump in salary.
There's also an argument that the Blue Jays already have top-of-the-order bats (Tulo, for instance). Spending more on someone who is better than Jose, Edwin, Josh, Troy, etc., will cost a lot. This player certainly isn't available on the market, and any trade cost would be pretty hefty.
And how good of a reliever do you think the Jays can still just pluck off the market? Assuming the Jays were willing to just pay Bruce outright, that means they have 10M to play with. I'm not sure I'd be comfortable splurging 10M on a reliever when there's already a pretty decent pen starring Osuna, Storen, Cecil, et al.
Bruce could very well be an upgrade over Saunders, who seemed to be injury prone even before the sprinkler incident. If the costs smooth over and the prospect capital isn't too much, then I'd totally take Bruce over Michael who-knows-what-you're-getting Saunders.