"Retail quote" means exactly what it sounds like. "Retail" means the private or commercial sale of a product to a consumer, and "Quote" means the pricing or estimate of an item or service being given to a consumer. A "Retail Quote" is a price or estimate for an aircraft, a service provided from an aircraft, or a sale of services using an aircraft to a consumer, including taxes and end-of-user fees. For instance, if you were to buy a new aircraft from Boeing, you would request a particular retail quote for the aircraft in question.
Retail quotes can be adjusted to be more or less than the initial quote. When a consumer wants to purchase an aircraft, the retail quote given to them is usually for the final price of the aircraft, so the customer can gauge whether they are in the right price range. Most of the time, whoever is purchasing the aircraft would like to add features for convenience or comfort, and that could increase the price of the aircraft. Also, unforeseen factors like the rise or fall of materials needed to produce the aircraft can determine the final price. This is why retail quotes are often given before the aircraft's production, so that way the customer is not blindsided with hidden fees.
Retail quotes can be for the individual features on the aircraft, the engines, and the material used in or on the aircraft. Retail quotes can also be for the services provided by the aircraft. A company that specializes in the hiring out of pilots can also provide a retail quote for the pilot’s services, although this is not common. Because retail quotes include end-of-user fees and taxes, they are typically referred to when a company is done with a leased product and wishes to purchase it. A retail quote would be given on the final price of the aircraft, along with any applicable fees that are currently for that aircraft.