Jefferson's opt-out and lower-salaried return means the Spurs will save about $17 million in salary, luxury tax and tax distributions this year (if one presumes Splitter was coming regardless). Jefferson's new deal cost $31 million after this season, which is all we care about since the Spurs were paying him in 2010-11 either way. Subtract $17 million from $31 million and you end up with Jefferson's deal as a three-year, $14 million extension, which seems eminently reasonable … if you were going to prearrange such a thing.
So the Spurs ended up with both the best and worst contracts of this offseason. But on balance, they're paying $13 million a year for the next three years for a Splitter-Jefferson combination. I'd take that deal any day, and between it and drafting James Anderson, I think the Spurs are in much better shape for next season than many people realize.