For the Pirates, a salary dump on two aging vets, an upgrade as SS, and Bay, they won't be able to resign when he's up for Free agency. In return the get an upgrade, OC for Wilson. An upgrade in the catcher position. one good young pitcher on the verge of ace status, one of the top Minor league SP prospects there is, Rivera, a decent outfielder, Kotchman, a good prospect that's been idled by an illness, and a good veteran reliever.
The ANgels get Bay of course, a guy they can afford to sign to a long term deal, and two aged vets to help out, and Wlson isn't much a downgrade from Cabrera. Napoli can be replaced with top prospect Mathis. Giving up two very good pitchers hurt, but for Bay, it's worth it.
Pirate fans pretending they can keep Bay are living in an illusion with the big $ teams (and Bay's agent) just chomping at the bit to pounce when he hits free agency.
The Pirate fans have to be realistic. The Pirates basically have to try and be competitive by being like the A's or CLeveland. Build a good young farm system, either sign their future stars to long terms deals very early (too late for Bay) or trade your star guys a year or so before their due for free agency. Hope you can piece together enuf good young kids, the players you signed to long term deals early, and the occassional not too expensive veteran players to stay competitive and keep the turnstyles turning.
When small markets team loses or trades very late their cheap star, they're basically wasting an asset. Oakland and Cleveland are very good at this sort of small market dillemma, that's why they are often contenders and in the series, the Pirates aren't and that's why they haven't been good since the days of Stargell and Parker.