My Domain List plugin allows users to make an offer on each domain.
Code Sample for Standard Version
[my-domain-list-portfolio size="medium" show="registrar,expires,price,offer" /]
Code Sample for Pro Version
[my-domain-list-pro size="medium" show="registrar,expires,price,offer" /]
The user will be presented with the following modal form once the Make Offer button is clicked on a particular domain.
The site owner or admin will be able to manage the offers from the WordPress Admin Dashboard.