The price for real estate software development can be very different from an investment. This can be influenced from different factors such as the purpose and complexity of the project, the technologies used to do the work, and the location and the expertise of the team, and the timeline of the project.
Nobody can estimate within $ 10,000 - $ 20,000 price zone an easy real estate website with basic functions alone because it is necessary to take into account the cost of a sophisticated software solution that can offer customers an AI-based search for properties, virtual tour, and advance analytics for, which hundreds of thousands or millions shall be spent.
I am of the view that it is much better if you and your software development company or software professional have that conversation so that you have a more precise estimate based on your very own requirements.