Given that global routing table is bloated because of site multihoming, where the site uses multiple ISPs within a city, costs of long-haul fiber is irrelevant.
I suppose smaller multi-homed sites can and often do take a full table, but they don't *need* to do so. What they do need is their routes advertised to the rest of the internet, which means they must be in the fancy-and-currently-expensive routers somewhere upstream.
This is where the cost of long-haul fiber becomes relevant: Until we can figure out how dig cheaper ditches and negotiate cheaper rights-of- way, there will not be an explosion of the number of full-table provider edge routers, because there are only so many interconnection points where they are needed. Incremental growth, perhaps, but physical infrastructure cannot follow an exponential growth curve.
Not entirely accurate. Most of the reduction in cost/mbps that has occurred over the last couple of decades has come not from better digging economics (though there has been some improvement there), but rather from more Mpbs per dig. As technology continues to increase the Mbps/strand, strands/cable, etc., the cost/Mbps will continue to drop. I expect within my lifetime that multi-gigabit ethernet will become commonplace in the household LAN environment and that when that becomes reality, localized IP Multicast over multi-gigabit ethernet will eventually supplant HDMI as the primary transport for audio/video streams between devices (sources such as BD players, DVRs, computers, etc. and destinations such as receivers/amps, monitors, speaker drivers, etc.). There are already hackish efforts at this capability in the form of TiVO's HTTTPs services, Sling Box, and others.
As it costs less than $100 per month to have fiber from a local ISP, having them from multiple ISPs costs a lot less is negligible compared to having routers with a so bloated routing table.
For consumer connections, a sub-$1000 PC would serve you fine with a full table given the level of over-subscription involved. Even something like Quagga or Vyatta running in a virutal machine would suffice. Or a Linksys with more RAM. Getting your providers to speak BGP with you on such a connection for that same $100/month will be quite a feat. Even in your contrived case, however, the monthly recurring charges exceed a $1000 router cost after a few months.
Simpler solution, let the providers speak whatever they will sell you. Ideally, find one that will at least sell you a static address. Then use a tunnel to do your real routing. There are several free tunnel services and I know at least one will do BGP.
Enterprises pay several thousand dollars per month per link for quality IP transit at Gigabit rates.
Since this isn't a marketing list, I'll let this one slide by. Owen