yes it is. if the report is true, that $500,000 per year number has been mentioned by several wrestlers and reporters over the years on podcast, interviews, etc.. Ryback said the same thing. he turned down a 3 year, $1.5 million contract. the $500,000 per year is their "top guy" minimum downside and they can make even more than that depending on booking and merchandise.
guys like Rollins, Reigns, etc. likely have guarantees double that ($1 million per year, etc.), but the $500,000 minimum is very common.