The Scotland striker has enhanced his reputation and fuelled play-off aspirations at Ewood Park with nine goals in seven matches. West Ham United, Stoke City, Sunderland and Fulham are among Premier League clubs keen on the forward.
Bowyer said: "It would have to be an astronomical offer because the owners have said to me he wouldn't be for sale.
"Goalscorers are worth their weight in gold. When I was offered the job, my first question was about Jordan and they said, 'No, we're not selling him'. Figures of £6.5m were mentioned in the summer, but he's got better, so how does that make economical sense?
"When the window closed and we knew he wasn't going to be sold, it gave everybody in the club a lift. No doubt when we get to January it will all start again."
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