Maybe you meant "SO this is priceless" not "BUT this is priceless."
Because if you say "he's not dead yet but this is priceless" it sounds like you're saying "this is priceless in spite of the fact he's not dead yet." As if him being dead would make it funnier.
However, "he's not dead yet so this is priceless" might imply "i can say this is priceless since he's not dead yet." But... I'm not sure if that's what you were trying to say either.
I say you could have left the death out of the title, but admittedly, I probably wouldn't have pointed any of this out on my own at all.