They use Cost Of Revenue because they are selling their IP to customers. IP is usually on the books for an amount that is nowhere remotely close to the value of the IP unless it was recently purchased by another company. To properly calculated COGS you would have to treat IP like direct materials where every sale decreases inventory which through WIP decreases direct materials. The value, useful life, and amount of sales off of IP is completely in the air unlike what is needed to treat like direct materials.

Instead they use COR (cost of revenue) which is essentially what it sounds like. If they had no revenue they would not have these costs. This of course is manipulated via absorption, variable, or other costing methods. So, essentially it really is a best guess.

For example IT is usually a G&A expense... but in the case of a program hosted online, the customer is essentially paying for the past work done by some IT guys and the current work done by IT guys until the end of the service period.