It's very difficult for Bancor's price to increase. I have seen this time and again whenever somebody buys a large chunk of BNT on Bittrex and pushes the price up within minutes, the automated arbitrage bots bring the price down by arbitraging against the smart contract. I don't see how the price will increase.
So why dont they buy from smart contract in first place?
Even if they buy from bittrex and arbitrge do their job buying cheap token in smart contract thus bring the both price to equilibrium there is still increase in price.
More token bought, higher the smart token contract price.
If you expect the manipulation pump n dump like others coin/token that can be done with merely few hundred btc... that not gonna happen with bancor.
Smart token contract cant be manipulate, the price will only increase with increase in token number.