I don't disagree with you. But just like in real life, markets are full of suckers.
You can't tell people not to overpay. The right price is what someone is willing to pay.
Player prices oscillate in BB just like the price of Vodafone oscillates in real life. It does not mean that Vodafone traders are stupid. That's just the nature of auction based markets.
A liquid market (more people) will have less price discrepancy (technically prices are less volatile, not sure about your background here, so I'm refraining from doing trader talk)
A market where at times there are less than 500 players is not liquid at all, hence more inefficient and with more price volatility. Traders can exploit that. It does not mean that other people are stupid.
At the end of the day, a "stupid" guy that pays 700K for a player worth 400K and goes off to win the title is not stupid at all. The other people in the league were blind to the opportunity and lost the title.
The idea of the BB is that if you have money in the bank you got to use it to win, you are not encouraged to hoarde money like in HT.
//elboss