From his website:

Shotgun Barrel Work

Sleeving- Double Barrels:

12ga., 16ga., or 20ga.: From $2000 + Blueing and Engraving

Tubes for above ​sleeving job: From $600

New Ribs, if needed, for above: From $1000​

Doesn't mention 28 gauge. Buddy had a gun sleeved by him. Saw pictures and it looked like the seam was invisible. Make sure you get someone who can match the blue on the sleeved section and the original section perfectly.