My husband and I will be travelling to Croatia this fall. We stay in Dubrovnik (in the Old Town) for six nights and plan to travel to several of the islands, go to Lokrum, Cavtat, and, perhaps, a few other places. I looked at the Dubrovnik card (7 days) - which would allow us to space things out over our time there (and avoid high traffic cruise travellers), but, when I add things up, I am not sure that we would be any further ahead with the card than we would be just paying as we go (unless we were using the bus a lot, and I wasn't sure that we would need to take 10 bus trips - I think we would need it only for going to the bus station or ferry terminal in Gruž). Am I missing something? Have others found it useful to have?
We got a 3 day card. It was more than enough.
Definitely get at least the 3-day card. It's 230 Kn, and includes the wall walk (which is 150 Kn itself). It also includes the Franciscan monastery and museum (well worth seeing), a number of other entrances, and is good for 10% off in many restaurants. So even if you don't use the bus that much, it's worth it.
The only way to look at this objectively is to do the math on the sites you are likely to see, add up their costs, and compare to the value of the card (it sounds like you've done that and already came to a conclusion). Many people buy these cards almost reflexively, and that's why these cards make a good profit. From my own experience, the card caused me to visit some museums I would have probably not visited were it not for the card because I didn't know about them otherwise. Every one of these city cards ropes in some marginal sites because that's the only way they can drive tourists to them. In Dubrovnik, I really did enjoy these smaller museums though. My takeaway though is to do the math because anecdotal evidence is just that. I am a much more critical shopper than I used to be in the past, even for small-potatoes things like these (they do add up over many trips). Good luck!
3 day card is great value, just organise in advance.