I stand to be corrected but was there really an agreement? From what I remember he, Arsenal and us agreed on a deal only for Arsenal to renege at the death. We were pissed with Arsenal and told the media that we wouldn't go above £20m. The only thing that changed this time around is united came to Sanchez and his agent with a desperate offer. There was really no need for any further "agreement" after the failed move in summer as we were convinced that Sanchez wanted us and he was also convinced that we needed him.
Our management was expecting him to live by his previous commitment - he's backed out of that.
Which is fair.
Now, having broken his word, we're no longer interested.