Pat -- I checked and there are three tiers, Blue, Blue Plus and Blue Flex or something similar in name. The price for dates I looked at comparing Blue which is no free checked bag to Blue Plus which includes one free checked bag was a price difference of $15. Better than getting the Blue fare and having to pay $35 for checking a bag.

We bought our inbound tickets on 6/28 when one free check in bag was still available. Our roundtrip fare each is mid $400s, currently the roundtrip fare for same timeframe is $620 using Blue Plus tier, which gets you a free checked bag in both directions.