Tier 1 operators do not do "best effort" really, at least not in their cores (and they have the SLAs to back it up). They buy hugely expensive top notch gear (Cisco 12000 (and now CRS:s) and Junipers) to get the big packet buffers, the fast reroutes and the full routing table lookups for each packet to avoid the pitfalls of flow forwarding the cheaper platforms have.
When 12016s are on ebay for $12,000, even a low budget "tier 3" can afford proper routing gear... It's not as if the Internet is still powered by 7507s! (Well, a large part still is. :-)
Now, how will this translate in cost compared to DWDM equipment and OPEX part of the whole equation?
I am starting to see some interesting long-distance 2.5Gbps CWDM gear offered by European manufacturers, with 70km and 100km distance ratings. This stuff sells for a fraction of the price of equivalent Nortel/Ciena/Cisco ONS gear. Lots of optics companies are making 70km rated SFPs in 8 or 16 wavelengths now. So far it only runs at OC-48 speeds, but 10Gbps will be coming soon.