$600 and up. Depending on how much you are wanting done. A maximum effort deal could near $1200.
Or more. I copied this from the web page of a fairly well known head porter from the Midwest.
Hand head porting
• Small block applications $1400.
• Big block applications $1500.
• "Econo" porting $750, includes valve job, chamber finishing, throat sizing, short side reworked, openings squared.
The following is performed on all hand ported cylinder heads
• Disassemble and clean
• Fully Ported (All chambers, intake and exhaust ports)
• Custom Multi-angle Valve Job (Sunnen VGS)
• Valves refaced w/intake backcut (Sunnen VR7000)
• Surface mill to MLS finish (Winona CBN)
• Flow testing (SuperFlow 600 w/Black Box)
• All valve springs checked for pressure (Buxton digital)
• Assembled (Spring pressures/install height listed on invoice)
• Bagged for install