Generally speaking three letter domain names are more popular than other long word domain names, especially three letter and word domain names, such as: PDF.ai. Just recently, the domain name PDF.ai was used by its founder, Chen, for an artificial intelligence-driven service.
The service takes Adobe PDF files as input, processes them, and provides users with the ability to interact with the content through ChatGPT-level robots.

In recent months, Adobe has also offered a similar subscription-based service for PDF files built into its Adobe Acrobat software. He is preparing to sell the PDF.ai domain as a package with the program.
Damon Chen seems to be getting a lot of lowball offers, most of which are only for the domain name, not the domain name and service. He got tired of this and listed the domain for sale on Dan for an initial price of $20,000,000.
The talented entrepreneur found that since Dan uses its own DNS for active services, he increased his asking price to $25,000,000.

Chan is well qualified to ask for millions of dollars for a service he created himself; for reference, according to NameBio, he paid only $610 for the domain.
Note: NameBio records appear to be the seller's acquisition cost; Damon Chen mentions that he acquired PDF.ai for $9,899.

Clearly, Dan is not the most suitable platform for selling multi-million dollar assets that may include website content.