That might apply in a league where you can amortise that loss over a whole bunch of games but in a single-shot knockout game, I'd expect a professional team to keep fighting even at 5-0 down - much as the Brazilians did in the second half. If it weren't for Neuer's outstanding saves, they could have had 3+ goals in the first 15 minutes.

(Although the league sometimes doesn't work like that either - I remember listening to Spurs vs Man Utd when Man Utd went in at half-time 3-0 down and ended up winning 5-3 in what is possibly the most epic half of football I've heard in 30+ years.)