Ellis, who was at the helm when Villa paid Brighton £500,000 for Barry, said: "If Gareth goes, and I fear he will as Steven Gerrard has been begging him to do so - then right now I wouldn't sell him for less than £15million.
"I am proud of the fact that we took a bit of a gamble and paid £500,000 for him and Michael Standing 10 years ago.
"On the financial side at least, paying half a million for Barry and selling him for £20million - hopefully if that is the sale price - is not a bad deal.
"If I was advising Liverpool, I would say 'dig deep' because he is such a good asset. It will be a big loss to Villa and I would fight like hell to keep him - but of course I am no longer there."
Ellis can understand Barry's desire to play Champions League football but knows he will be difficult to replace.
He said: "He sees the Champions League football as something that he should be in. His friend is Steven Gerrard, they room together for the internationals and as such he is being persuaded to go there.
"But, like I said, it will be a big loss to Villa should he go."