I guess if you broke down the actual assets of owned buildings and land and equipment (towers, tower leases they actually make profit on vs. pay) you could isolate that from the cost of each stations worth and get a reasonable figure.
Keep in mind that iHeart is more than the 840 radio stations. The streaming platform is worth more than $1 billion. The Outdoor advertising part is worth another billion. They do a number of concerts, festivals, and awards shows. They sold the towers and land to Vertical Bridge a couple years ago. But they probably own a lot of studio buildings, equipment, and various contracts. The cash flow of just the radio stations is over a billion, so I'd say the $8 billion figure sounds right.