yea thats the one
people seem to forget wholesalers and ISP's are businesses, the more products they offer the more money it costs them to administer those products. there is also little to no cost difference between some of those products so why offer something for a slower speed when you can offer something for a higher speed for the same price?
The LFC cost is the major part, but certainly not only cost input. Service providers are not tied to LFC speeds even if often this will seem most logical. For example, a quick look shows these guys have 100/100 and at a mid way price point - http://www.worldnet.co.nz/residential/residential.php?network=UFB The cost of administering products not tied to external changes (like Chorus) is quite minimal. Again, what the OP is asking about is not at all unreasonable with the proliferation of cloud storage requiring decent upload speeds.