Here is another price list that has the 4CX600JA.
http://www.elexs.com/2Xmtg.htmIf the rfparts price made you choke, this one will make you lose your lunch completely.
$2125.
I often see prices for tube in these industry supply companies that seem real high compared to what you can get on ebay, and even higher than the typical "ham" price.
I can't find anything on ebay for the 4CX600JA, however.
What you charge will probably come down to how much you like the guy that wants them.