So to that list I would like to add LPCs, Laptops Per Child, with the base unit representing $100, the goal of the OLPC project. For example, the base price of the newly announced MacBook Air would be 18 LPCs, or an iPhone would be 4 LPCs.
Now you can measure your expenditure in units that tell you how many poor children you could be helping, instead of gorging yourself on the latest gadget.