The winger joined De Trots van Zuid in the summer following an underwhelming first season at Vicarage Road and has helped the team climb clear at the top of the Eredivisie.
Berghuis' performances have even earned him a return to the Netherlands camp and questions are starting to be asked about his next move.
However, the 25-year-old believes he will not be staying at De Kuip as he does not think they will be able to afford anything near the 6.5m euros the Hornets paid for him.
He told De Telegraaf: "As it looks now, I am going back to Watford. The club has bought me from AZ for 6.5 million.
"But what I would cost Feyenoord now, I do not know."