the cost of a "custom_json" operation is now directly proportional to its size; meaning, reducing the content only to the essential elements will be a RC-saving measure.
But then isn't that forcing dapps to write less, and thus not meet their use case ? Or we expect, they power up to have sufficient resource credits to take full benefit ?
Apps have multiple solutions: be more thrifty with the amount of information they write, delegate RCs to their users or suggest their users to power up more HIVE, ...