From the New Yorker:
It was as if there were a kind of conspiracy in the basketball world about the way the game ought to be played, and Ranadivé thought that that conspiracy had the effect of widening the gap between good teams and weak teams. Good teams, after all, had players who were tall and could dribble and shoot well; they could crisply execute their carefully prepared plays in their opponent’s end. Why, then, did weak teams play in a way that made it easy for good teams to do the very things that made them so good?
[...]
David’s victory over Goliath, in the Biblical account, is held to be an anomaly. It was not. Davids win all the time. The political scientist Ivan Arreguín-Toft recently looked at every war fought in the past two hundred years between strong and weak combatants. The Goliaths, he found, won in 71.5 per cent of the cases. That is a remarkable fact. Arreguín-Toft was analyzing conflicts in which one side was at least ten times as powerful—in terms of armed might and population—as its opponent, and even in those lopsided contests the underdog won almost a third of the time.
[...] What happened, Arreguín-Toft wondered, when the underdogs likewise acknowledged their weakness and chose an unconventional strategy? He went back and re-analyzed his data. In those cases, David’s winning percentage went from 28.5 to 63.6.
[...]
Arreguín-Toft found the same puzzling pattern. When an underdog fought like David, he usually won. But most of the time underdogs didn’t fight like David. Of the two hundred and two lopsided conflicts in Arreguín-Toft’s database, the underdog chose to go toe to toe with Goliath the conventional way a hundred and fifty-two times—and lost a hundred and nineteen times.
Not sure what you mean by "cheap".
"Cheap" is a term used in the Playing to Win essays. It generally refers to a tactic that is uninteresting or repetitive but successful.
The example used in the essays is repeating the same move over and over in Street Fighter.
(Edit) The example from Eurisko is that making ships that sink themselves is "cheap" because ships in a real war wouldn't do that. It is a valid strategy according to the rules of the game but invalid according to extraneous rules that have no bearing on the game.