What are 660 Holley center squirter cores worth?

A customer, came in. Had bought a BBC tunnel, with 2 660 center squirters.The O'crappy's sold him,standard double pumper kits.(1st fail!). I take a few minutes, explaining the hit of center squirters.His eyes ,OPENED!
Needless to say,what is a pair of 660 c.s. cores worth?