"Cheap mother" idiom [closed]

That is a wry way of expressing that they welcome all feedback, including criticism.

If there is any idiom to be revealed, it is the general your mother ____, for instance:

• Your mother is so poor, she put a milkshake on layaway.
• Your mother is so fat, when she sits around the house, she sits around the house.

From the link:

A maternal insult (also referred to as a yo momma joke) is a reference to a person's mother through the use of phrases such as "your mother" or other regional variants, frequently used to insult the target by way of their mother.1 Used as an insult, "your mother..." preys on widespread sentiments of filial piety, making the insult particularly and globally offensive.

Edit:

As Dave says in comment,

The other idiom is "___is cheap", referring to them being an inexpensive prostitute.