Richard Kaplan wrote:

This practice is common with lots of mail order products, especially
electronics. Look though any computer magazine and you will see "$CALL"
listed as prices for various electronic equipment.

It's also common with photography gear.

George Patterson
This marriage is off to a shaky start. The groom just asked the band to
play "Your cheatin' heart", and the bride just requested "Don't come home
a'drinkin' with lovin' on your mind".