Just because something is widely reported does not mean it's true. You can just as easily find reports which details the cost of the network at $220M, which is how much the city bonded for to build it. Furthermore the sources you cite yourself clearly states that of the $330M, $111.5M was a federal grant for the smart grid.

As to the smart grid project, that was a separate $232M project. https://www.smartgrid.gov/project/epb_smart_grid_project.htm...

Of those smart grid investments, only the Backhaul Communications part could conceivably (in part) be attributed to the fiber network buildout costs. In no way can 100% of the federal smart grid grant be seen as a subsidy to the fiber network. Even if you subscribe to conspiracy theories about the power side secretly subsidizing the fiber side, that 100% subsidy theory just does not survive the collision with reality. Given how litigated this issue has been, there's no way the opponents would let a hundred million dollar misuse of federal grant money slide.

Either way, no matter what dollar cost you peg the fiber network buildout costs at, your $5,000 cost per subscriber is plain wrong. The correct figure is closer to $2650, but it's still not even close to $5,000, even if you slap on an additional hundred million dollars in costs.

This obviously also makes your payback times wrong.

To give some context to EPB fiber's costs, ten years ago Verizon paid $850 per premise passed and an additional $880 per premise connected. These are in line with EPB's costs if you assume a 50% take rate for FiOS.

Just to rub it in on how wrong your estimate of $5,000 per subscriber is, the very source your cite yourself states that the average cost to connect a new subscriber to EPB fiber is $1,200.

But, wait, there's more!

Your analysis on the economics of fiber networks just crumble when you look at the annual report of EPB. Here's the punchline:

- operating expenses include debt service!

EPB fiber pays EPB $10M per year for the use of the fiber network. This is enough to cover the costs of the $220M bond. In fact it covers half of EPB's whole debt service. Incidentally EPB fiber's operating income would more than covers the remaining debt service with change to spare.

In other words your assumption of 60% in operating expenses excluding debt service is just plain wrong and all your calculations are wrong.

And that's even before factoring in the fact that service at $70 per month usually does not include cable tv. This in turn means that a large chunk of operating expenses for that service can be excluded, as cable tv rights are a major cost item.

All in all, even assuming debt service is included, 60% operating expenses for a fiber network is not a given.