OP I'm with you. D1 pricing has been going up and up for the past few years. I blame the TATL JVs across all airlines and the reduction in % of D1 seats / total seats, a trend that is only getting worse.
To those who say "be flexible and look at other airlines"; yes but; you have to be WAY more flexible than you used to in terms of dates, and each airline has its pros and cons, and the reason why one comes to DL is because one likes DL for whatever reason. E.g., I rarely fly VS on an overnight flight TATL since their beds need to be "made" and that takes out precious sleep time.