Good value for the money means different things to me.
1. All out low price. I know when I get a Carnival cruise for about $50.00 a night, it is a good value for the $. I also know what to expect for food, service, entertainment and the ship. Oh and lets not forget all the kids running around on Carnival. Kind of like shopping at Walmart. Good cheap fun and a bit tacky but not where you want to spend a lot of time.
2. What you get for your dollar. High end luxury and service. I know when I book Celebrity it will cost me more then Carnival but I know I will have a different experience. I know the ship will be elegant, service will be top line, good food, lectures, nice cabins with flat screens and lots of storage, Bath amenities, (free cocktail hours every night, free laundry and free cabin upgrade from the loyalty program benefits), more space on the ship per passenger so it does not feel crowded and I also know I will be with higher grade fellow cruisers.
For me the Value depends on the experience I want at that time. What I will put up with for a few days to a week is different then what I want for 2 weeks or a month..