Dean Bubley: How much data in that bundle?

Dean Bubley posts some interesting questions about bundling mobile services at his Disruptive Wireless blog. Regarding an advertised bundle he recently saw that included voice, videotelephony, texts, MMS and downloads, Bubley asks "how the accountants and management work out the value of each element. Is it based on that element's included allocation in the bundle? Is it based on the actual usage of those allocations? And exactly how do you work out the relative implicit value of say, actually using 800 texts vs £7 of downloads vs. all 150 voice minutes?"

On the subject of ARPU, Bubley writes, "How exactly do carriers work out the % ARPU attributable to data services, when most of those services come pre-bundled at a non-specified cost per message/download/video minute in a plan? Is there any consistency between mobile operators? Are these numbers audited, and if so, to what rules? Do the rules vary by country, or change over time?"

He then concludes that "Maybe everyone shouldn't be so surprised that mobile data ARPU percentages keep creeping up, as they're such an important and closely-watched metric.... and (perhaps) so easy to fiddle..."

Any ideas? I, as usual, have no clue. I just consume the stuff...