Thanks for the information. Can you tell me how you got these numbers? If I knew how to find out the fares for all the different classes available, then I could do the cost-benefit analysis and buy the best ticket for myself.

I know that sometimes I've flown Y and B at different times on the same route and had it be approximately the same price. However, I've never been able to compare Y and B prices for the exact same trip, since I don't know how to work the web site properly.