Yes it can be fixed. You need to find a welding shop to fix the crack. There might be some additional work done afterwards to ensure the head is true. It might need to be milled .010. I had it done to my heads, it is doable.
It's not usually expensive to have the crack fixed. but it gets expensive to have all the machining re-done after the welding. The head needs to be heated red hot to weld it. So you need to to a complete valve job on it after.