With the retailer asking for a phone number, I don’t see how it would ever be worth even entertaining. They will give you a discount once, then have and potentially abuse your information for years to come.

You can make an email rule to filter those messages to trash.

I have my phone set to only ring for people in my address book. It’s probably time to do something similar for email. Not in my address book? Straight to trash.

Yes - and a fair price would incorporate that.

Hence I doubt retailers will ever consider offering a fair price.