This lock in concept is prevalent and so counter to the concepts embodied by cloud. If cloud is supposed to turn computing into a utility like function, the only way lock in should work is via monopoly power.
Amazon and Apple in this case are banking on non-utilization of the space (most customers will not use the terabyte of storage) similar to the way AOL had very low concurrency on their dial up service, OR that they can use storage as a loss leader.
We are constantly seeing price pressures on the commodity aspects of our hosting services and that is why we are looking for new and unique ways to provide value. Whether that is through deep knowledge of the product/service or additional functionality that is complementary to the service. Examples include develop scripts to keep background ERP services running smoothly or integration services to enhance the value of our core product.
DropBox will have to do the same to survive because they are providing much more than core storage. Whether it is security, ease of use (drag & drop into your box), etc., the focus needs to be on what value do they provide to the end user for their intended use of the service.
ERP users don't buy cloud, they buy the anytime anywhere availability to their information. They don't buy TB storage or GB of RAM, but ways for remote salespeople to see customer notes or status of an order.
The data should always be owned by the customer and available to be moved anywhere at any time. We are fighting with SAP and another hosting provider for a customer that wants to move to our service right now and they were told they could not get their data until the term ended... unless they purchased a perpetual license. This is nowhere in any contract of policy from SAP but a blatant money grab and lock in tactic by an unethical provider. These people who try to lock in give Cloud a bad name.