It's probably an indication that your use-case is not a good fit for dynamo, or that you didn't adapt your use-case to dynamo, you're doing something "wrong" like trying to use it as a relational database. I've experienced some of these pains as part of my dynamo learning curve.

For example by changing my query strategy I was able reduce the provisioned write units from 1900 to 150 (write units dominate the cost).