I think a big part of the problem is that chairman base their prices on the fees paid by the mega rich clubs. Just because City by Sterling for £50 million, or we pay £36 million for Martial, it doesn't mean price can be set using those fees as a guideline. It's the market that dictates price and each player has an individual market. The same clubs aren't interested in every player, hence supply and demand is different for each player.
No big clubs were in for Berahino. In fact, it seems they only had one club bidding for him. If he was being that under valued, then surely some other mid level club would jump in. But no Prem clubs, such as West Ham or Newcastle made a move. No foreign clubs came in. Everyone is being critical of Berahino and rightly so, but at the same time, we have to recognize that currently, some chairman are valuing their players based on an odd valuing system. This is why it's so much better for English clubs to buy abroad. Their leagues tend to only have 1 or 2 rich clubs, whilst we have 5, that give chairman a totally false idea of what their players are worth.
Berahino is only worth £25 million if a club is prepared to pay it and unless one of us, City, Chelsea, Arsenal or Liverpool are interested, that isn't going to happen as he's not good enough for interest from those clubs. At the end of the day he's not even a full international. He's never played CL football and he's never scored that many goals. A similar player in Germany or France, would probably cost another club in that league around £10 million. Berahino is Prem proven, but he's not proven to be top class. He's alright and his value should be based on him being "alright," and not on how much the world richest clubs paid for other players.