It may have been "unreasonably high" but the Cubs are pretty much the only team (you can probably say Boston as well) that needs a legit ace, and they didn't accomplish that.
Jed just better hope the starting pitching can hold on throughout the remainder of the season, and that Boyd/Imanaga can perform well in the postseason. If they don't, then this was a failure.
I'm sure Miami's asking price was high for Alcantara, but he can still have the ability to be an "ace" pitcher again when he returns into form. You add that with getting Cabrera, and you're able to have a postseason rotation with Alcantara, Imanaga, Boyd, Cabrera/Horton. I don't feel confident with Taillon/Assad starting a postseason game.