I'm totally happy if we've offered as much as we think Sanchez is worth and he chooses to go elsewhere, even if it's Utd. £35m is not "still great value" if we end up paying him £400,000pw. The actual value of the transfer is far higher if we suddenly have De Bruyne, Sterling, Sane, Jesus, etc. all believing they should all be on comparable wages, not to mention any future signings we make.
Sanchez is 29 and will only decline in form and value if he did join us. I'd love to sign him this window, but if we're convinced it's a bad deal then i'm perfectly happy for Utd to take him.
Sure, we may end up paying £80m-£120m for an alternative in the summer. If that player is on half the wages, is in his early 20's and grows with the team in the way that De Bruyne, Sterling, Sane, etc. all have then that's a way better deal than this one for Sanchez looks.