http://kavassalis.com/2011/04/the-internet-isnt-free/

I want to sell enterprise grade DSL to businesses who demand a reasonable 10mbps guaranteed. This is a very common scenario. If I split my gigabit link up to 10megabit customers, the most I can fit on it and guarantee their performance is 100 customers. If we take our cost to buy just the transit, ignoring any of the related costs, we’re going to run $40-80/customer.