The value depends on how you look at it.
Many would argue we have already replaced Sterling so getting back essentially what we paid after having great service is a no brainer. If we don't sell it seems likely he runs his contract down. I know we did it with Garcia but I would be shocked if we allow it again.
Torres, the risk you take is "losing" his focus and energy to play for City. He could go on strike, refuse to train and do everything to not play if thats what it takes to get his move to Barca, don't think he will but you never know.
I don't think Pep can be arsed with that and will simply let him go.
I expect City won't do that because it sends a signal to all other players and clubs that if they just ask to leave they will get big discounts on transfers. It's not just about an isolated deal then but about principles, which is bigger picture and long term.
Example: it was when Garcia mouthed off in public that he wasn't ever signing a contract that City stopped negotiating his transfer and held him to his contract.
Torres, by contrast, appears to have privately asked in a respectful way. Leaks all coming from Barcelona side, standard. We'll see if he ever does what Garcia did but if he wants the move it would be a bad idea. It would change the equation for City by making it about principles again.