How much for a good valve job on Edelbrock Aluminum Heads?

I called a guy about some some used small block Edelbrock Preformer RPM heads (closed chamber) he had advertised for sale.

He said they were sold but that he had another set he would sell, but that they could use a good cleaning and maybe a valve job.

I haven't looked at them yet, he wants about half the price of new heads...so i wondered what the going rate these days is for a valve job?

Thanks in advance,
Paul