The level of Solo screwing differs from cruise to cruise. You seem to have landed several cruises that have a lower "upcharge". In my case, I'm looking at a Transatlantic and then a Italy and Croatia back to back. The overcharge for the Transatlantic is only $150 (2x + $150). The overcharge for the Italy and Croatia is 2x + $800, which is silly.
Besides others on this thread who have also experienced this issue, I have several proof points:
1. My partner experienced the person in future cruises stating that this is the new policy.
2. My cruise planner told me as well that they received this policy about 3 months ago, and agreed that it makes no sense.
3. I DID call Celebrity directly, and their own Rep told me this new policy is to address the fact that Solo's don't "buy multiple drink packages, or multiple wifi packages, or multiple specialty dining outings, or spend as much in the Casinos".
Not sure what additional proof you require, but I'm happy that this hasn't affected you YET.