Let me understand your reasoning;
Because UMTS provides better encoding and can deliver more bits / cycle, ON THE RADIO LINK, you deduce that the TOTAL cost to deliver an IP service must come down? Even if you agree that to carry the required increased bit-rate on the back-haul will be substantially more expensive?
So, we need to:
1) Build a new 3G network with no common equipment with the 2G network.
2) Upgrade the new network to HSDPA within 18 months of initial roll-out.
3) Increase back-haul capacity by a huge factor (~20+). Forcing transmission costs to go up by the same factor.
4) Increase international connectivity by a huge factor (~20+). Again, costs go up by the same factor.
5) Increase all in-line and real-time systems to handle the increase in capacity. Again a corresponding increase in cost.
And you actually believe it's now less expensive to deliver a bit over HSDPA compared to GPRS....

So again, please prove how UMTS is driving the total cost down to deliver a bit to you. Please explain how UMTS makes is less expensive to deliver a 1800Kb/s service vs. a 80Kb/s service.
Please give us comparative costing to deliver a GPRS service vs. a UMTS service. You can use an assumed user base of 300K, spread across the major centers.
By the way, nowhere in the links you posted can I find any information on the total cost to deliver a service. Have you actually read the links you posted?
Awaiting your financial models with anticipation.