The old Sioux valve grinding machines had an optional accessory for resurfacing rocker arm tips. It held the rocker square with the grinding wheel and the fixture was adjusted to match the radius of the tip. Once the fixture was set up properly all the rockers could be reground in a matter of a few minutes. Chances are that the shop that was mentioned that "reconditions" rockers is using a fixture like that and making an outrageous profit doing what us oldtimers did as a matter of routine on every valve job we did.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!