Where I work (PagerDuty), we follow up with everyone who cancels -- my favourite was "I only signed up to be alerted by a script as soon as PAX tickets went on sale" He got them.
Maybe we should start trial runs of this feature..
o Send me an email if the price drops below $_____
o Send me an email and put 1 item in my shopping cart for me if the price drops below $_____
:)