Fred, the issue is that the 260 is a lot straighter walled case than the Swede. The Swede is about .020 smaller at the shoulder. This means the smith may need to cut off most your chamber just to get the Swede reamer to clean up the 260 chamber. He would cut off the barrel threads and have to re-thread it. That's why they are giving estimates that are higher than the barrel is worth.

Sell the 260 and buy a Swede. Or, trade if someone is willing.