You sound a bit defensive here
Look, Liverpool has the right to value him at whatever they want- but if your honest, Sterling is not yet the calibre of player that's worth £40 or £50M - I don't care who he plays for, he just isn't. He's also a big disruption in the camp at the moment, so therefore it seems to make more sense to offload him if some fool is willing to pay £40+ million for him.
Also, I used De Gea as a comparison. De Gea is proven and will get better, plus he's already won the league etc. In that case, our valuation for him makes more sense than LFC's for Sterling - who hasn't exactly proved himself yet. So therefore, if you're getting £40+ million for someone who hasn't even performed to justify even half that amount, then that is great business and the club should take it whilst the offer is still there.