I haven't yet heard the point that if .org prices go up too much, nonprofits could abandon it and switch to .ngo, which is better anyway. Many will keep their .orgs even if prices go up 10-fold or more, but what percentage is that from all .orgs?
To quote Michael Bolton from Office Space:
Samir: Hmm… well why don't you just go by Mike instead of Michael?
Michael: No way. Why should I change? He's the one who sucks.