A frequent rate change indicates that that the reader has sparse or non-consistent customers. A reader that has a steady flow of existing clients and new customers wouldn't need to change their rate so often. I can understand after a certain amount of time passes and they want to raise their rate by a certain percentage (think, adjusting to inflation), then that would be logical.
Most likely during the real high upswings these readers are trying to 'make up' for lost income due to few calls from previous days.
My take. I've been around a minute or two now.