how much will it cost

[ride red 14]

about how much will it cost to rebuild my head on my 400ex

[GPracer2500]

Seems to me it will all depend on what parts need to be replaced/repaired.

Valves?
Valve seats?
Valve guides?
Valve springs?

Are the cam journals OK?
What about the cam? Rocker arms?

I realize you probably don't know what parts are bad, I'm just pointing out the best case scenario is probably substantially different than the worst case scenario.

[JOEX]

Don't forget the valve seals:p

And since the head is off, might as well port it too:D