I have the sense that there is a continuing flaw in the overall management thought process of the A's. I have watched the last few years of rebuild, sell off players for prospects (Harden, etc), go for it but then sell off when/if things don't work (Holliday and now Sheets). It seems the contigency plans maybe have too many contingencies.
Then I looked a bit at the Florida Marlins. With much less available in financial resources they seem to be at least marginally competitive and entertaining each year. They develop their own talent and trade for more, like the A's, but they don't delude themselves with hiring big dollar short tem players.
My hindsight suggests that Holliday and now Sheets will not work out well for the A's and the roster slots should have been used on someone who could be developed and is at least cost controllable for the next few seasons. Minor league free agents, the farm system, blocked major leaguers from other teams may be a better way for a lower revenue team like Oakland. I doubt the expensive, short tem players will sell many more admission tickets in Oakland than lower priced, readily available talent. Perhaps it is simply a case of management giving the public a more visible illusion of acquiring expensive players to try to improve rather than the more long term, but lower profile attempt to put a competitive and entertaining team on the field.