Jameni - There are so many other factors you are missing...
1) Licensing costs. Annual & upfront e.g. The idiots at CCK want $25mn for 3G services. No wonder only safcom provides 3G. Orange is testing it but only through 31 Dec 2009.
2) Infrastructure costs. Even base stations cost lotsa chumz if you cover an area. Add install costs, etc (unless your client pays). The trend is towards cheap or FREE equipment. See Zuku offer where 3k is for install but free equipment. Or safaricom's free modems.
3) Access Fees. Did you know that NCC charges you to access homes using fibre? Or any time you 'dig' on a street, you have to toa mbecha? And this is not even the 'chai'.
AK has built up the network over a few years. Safaricom is using their existing towers (not so much fibre) to expand their reach. Zain & Telkom/Orange are following Safaricom's lead.
I am not sure what the strategy from Sovaya, Tangerine or InstaConnect is lakini they are in for a tough fight.
BTW, all said & done, I think the wireless carriers (own network), KDN & those with their own cable system (Zuku & AK) will be the last ones standing!
Greedy when others are fearful. Very fearful when others are greedy - to paraphrase Warren Buffett