Armstrong is one of the leading scorers in England after netting 11 goals in 10 Championship games with Blackburn, and Rovers CEO Waggott claims that it could take a bid of up to £30million to entice the former Premier League champions to sell the former Newcastle United striker.
Speaking to Lancs Live, Waggott said: "We got a good price, albeit with a big sell-on, but he does what it says on the tin.
"When he's at it, he's a prolific goalscorer and I would think if any offers came in, it will be for Armstrong.
"Goalscorers keep you in jobs, don't they? They keep managers in jobs, they keep the fans happy and Blackburn had another decent Geordie striker when they won the Premier League way back, didn't they?
"If he can get anywhere near him he'd have had a decent career."