Dropbox hasn't spent the money apple has in R&D and software development to make a series of apps that work across different devices, let you edit photos, organize, store, etc.
Dropbox offers you space in the cloud to store your files.
It's cheap and simple like public storage.
Now imagine your own personal gallery space where you have a curator laying everything out beautiful, helping you edit photos simply, with so much organization that you can quickly find any of your thousands upon thousands of photos with a few flicks of your finger.
Now, given all this context, think Apple's pricing plan is still "whopping" compared to Dropbox's?