We haven't sailed on the Ruby in many years (2009) and I suspect the difference in price is due to it being an older ship which doesn't attract newer customers like the other ships do. We'll be giving it a try this fall once again and although it might not be a shiny and new as before I'm certain it'll still be fine.
This is the Princess we've been enjoying for the longest time although people wearing shorts at dinner is a relatively new thing.
We're not Club Class people since the special meals to us, don't warrant the extra cost plus our table is always waiting for us when we arrive. Why pay extra for a questionable service?
Officially, that statement is correct but from what I've experienced in the last 2 years, Princess is turning a blind eye towards those who like to wear them on casual evenings. Many guys choose to wear them in the DR on Caribbean cruises.