Why would you not do it? I feel like this base is not too far off. Carolina Obviously adds.
The add won't matter, because at no point would Carolina add enough to make it worth it to Pittsburgh. Value doesn't matter given where Pittsburgh is at with their window, as it's all about the on ice product. If you were talking Slavin, that would change things, but you're not for obvious reasons.
With Faulk, contracts is the easiest thing to point to (term, not AAV). But even just looking at the players, Letang is the better player. Nothing against Faulk (who I'd love to have), but he's not going to anchor the blueline. Nor can he even fill the minutes that Letang plays (ES/PK/PP).
Then there's the production aspect. Faulk over the last 3 years has 105 pts in 215 RS games. Over that same span (last 3 seasons), Letang has 149 points in 191 RS games. Again I'd love to have the guy as he's a better version of Schultz and can push the pace and transition the puck and he's on a great contract. But he too is a flawed player.