Not quite looking at it right. They did this deal, because they weren't going to meet Teheran's price. Personally, I sort of like the deal better for Boston and it sort of shows the premium that clubs are putting on top hitting prospects.
From Boston's perspective, they spent 1.8 million on Espinosa to land a cost controlled rotation piece with control and high upside who may have just turned the corner. With their budget, Boston can continue to make acquisitions like that in the future to fill in the gap.
San Diego gets a high upside pitcher who is maybe three years away from the big leagues. Nice piece, and similar to some guys Atlanta has grabbed, but nothing that is a sure thing.