Maybe you ought to spell Byte with capital B and bits with lower case b, e.g. GByte and kbit. Furthermore you should consistently use the same time reference in section 2.1 where you specify the costs for your national and international connectivity, e.g. use either only costs per year or costs per month. A coherent reference frame eases comparisons. We do consider this cost analysis very important. There is a problem though with the basic assumption upon which the numbers are based.
Many assumptions have to be heavily modified for other maintainers, especially commercial ones.
Nevertheless the methods specified can be taken as an excellent guideline for other calculations. Caching helps for hotspots, especially for transient ones where web servers are not scaled to take the load.