its easier to make profits when you have low trade bids (been there done that). but it can be quite hard when you have a larger amounts to trade with. you would not be able to rely on the internal market any more then.

also when you try to outbid someone in the orderbook, if both of you try to outbid each other, and one of you outbid each other much higher than the other, then the spread decreases fast. you dont need to outbid a person by much to have a more competitive offer. sometimes it makes even sense to take small breaks in trading so that who ever tries to outbid you then goes back to the original spread.